Property Development Feasibility Risks: 10 Costly Mistakes to Avoid Before You Buy
The most expensive mistake in property development can happen before you even own the land.
You find a promising site. The proposed development looks achievable, comparable sales are encouraging and your spreadsheet shows a healthy profit.
Then the real numbers start coming in.
The engineer identifies unexpected site works. Council requires changes to the design. The builder's price exceeds your estimate. The lender offers less funding than anticipated.
Suddenly, the development that looked profitable when you signed the contract is struggling to stack up.
The issue isn't always that the developer failed to prepare a feasibility study. It's that the study relied on assumptions that were never properly tested.
A property development feasibility study should tell you more than how much profit you could make. It should show you what could go wrong and whether the project can survive it.
Here are ten feasibility risks every property developer should investigate before committing to a site.
1. Assuming the site can accommodate your proposed development
A large block of land doesn't automatically mean a large development yield.
Zoning may permit townhouses or apartments, but setbacks, access, parking, site levels, easements and stormwater requirements can reduce what can actually be built.
Imagine purchasing a site based on a six-townhouse development.
After preliminary engineering and design, you discover that the required vehicle access and drainage infrastructure leave room for only five.
You've lost one potential sale, but your land cost hasn't changed.
That missing dwelling could represent most of your anticipated development profit.
Before you buy: Have the proposed yield tested against the site's planning controls and physical constraints. A preliminary concept supported by appropriate planning and design advice is far more useful than assuming the maximum theoretical yield is achievable.
Development potential is not the same as development feasibility.
2. Paying too much for the land
You can identify the right site, propose the right housing product and still make a poor investment by paying too much for the property.
This often happens when developers become attached to a site and adjust their feasibility assumptions to justify the vendor's asking price.
The better approach is to work backwards.
Start with realistic completed sales values. Deduct the full cost of acquiring, approving, constructing, financing and selling the development. Allow for the return required to justify the capital and risk involved.
What remains helps establish the amount the development can commercially support for the land.
This is the principle behind residual land valuation.
It shifts the question from “Can I afford to buy this property?” to “What can this development afford to pay for the property?”
Before you buy: Establish a maximum acquisition price based on the project's numbers—not the vendor's expectations or the amount a lender is willing to advance.
3. Treating an early construction estimate as a confirmed building cost
A preliminary construction rate is a useful starting point. It is not a fixed-price building contract.
Construction costs depend on the actual design, site conditions, specification, access, structural requirements and procurement arrangements.
A sloping site may require extensive retaining walls. Difficult ground conditions may require a more expensive foundation system. Limited site access may increase excavation, craneage and material-handling costs.
Developers must also understand what is excluded from an estimate.
Demolition, external works, authority connections and other associated costs may sit outside the builder's preliminary price.
Before you buy: Use construction estimates that reflect the proposed development and known site conditions. As the design progresses, replace broad allowances with project-specific cost advice and tender pricing.
A feasibility built around an untested construction budget is only as reliable as the assumption behind that budget.
4. Overestimating what the completed properties will sell for
Gross Realisation Value (GRV) is the estimated total revenue from selling the completed development.
A small error in GRV can have a substantial effect on profit.
Developers sometimes rely on the highest sale achieved in a suburb without considering whether the proposed dwellings will offer the same size, design, location, parking, outlook or level of finish.
They may also overlook competing developments scheduled to reach the market at a similar time.
Consider an eight-apartment project where each apartment sells for $75,000 less than the feasibility assumed.
That's $600,000 less revenue and, if costs remain unchanged, $600,000 less development profit.
Before you buy: Research genuinely comparable sales, understand the target purchaser and test whether the proposed product matches local demand.
Don't build your feasibility around the price you hope to achieve. Build it around a selling price you can reasonably support with market evidence.
5. Overlooking hidden site and infrastructure costs
Some of the biggest development risks are impossible to identify during a routine property inspection.
Rock, unsuitable soil, contamination, groundwater, flooding and inadequate utility infrastructure can all create additional costs.
Easements and title restrictions may also affect where you can build or how the development can be serviced.
For example, a proposed development may rely on stormwater drainage through a neighbouring property.
If the required easement cannot be secured, the developer may need an alternative engineering solution, or may be unable to proceed with the intended design.
Before you buy: Investigate title restrictions, easements, survey information, drainage, available services and relevant site hazards. Seek specialist advice where an unresolved issue could materially affect cost or development yield.
A site can have development potential and still be commercially unviable because of what lies beneath it, or what is required to connect it to essential infrastructure.
6. Underestimating how long the development will take
Every additional month can cost money.
Interest continues to accrue. Holding expenses accumulate. Construction prices and market conditions may change.
Yet early feasibility studies often assume that approvals will proceed smoothly, finance will be available immediately and construction will finish exactly on programme.
Property development rarely offers that level of certainty.
Council may request additional information. A design change may trigger further engineering work. A utility connection may take longer than expected. The builder may encounter delays.
Before you buy: Prepare a realistic programme covering planning, design, approvals, procurement, finance, construction, certification and sales.
Then test what a three-month or six-month delay would do to your finance costs, cash flow and development profit.
If your feasibility doesn't properly account for time, it doesn't properly account for cost.
7. Assuming the lender will fund what your feasibility requires
A profitable project is not necessarily a fundable project. Developers need to understand more than the headline interest rate.
A lender's valuation, loan-to-value ratio, loan-to-cost ratio, establishment fees, drawdown conditions, presale requirements and repayment terms can all affect the project's cash flow.
Most importantly, you need to know how much equity you must contribute—and when.
Imagine your feasibility assumes that a lender will fund a particular percentage of the acquisition and construction costs.
The valuation comes in below expectations, and the lender reduces its proposed facility.
You may now need to contribute substantially more equity than originally planned.
Before you buy: Model the proposed funding structure, including acquisition funding, construction drawdowns, fees, capitalised interest, monthly cash flow and peak equity requirements.
Test what happens if the valuation is lower, the interest rate is higher or settlement occurs later than anticipated.
A project can show a healthy profit and still run out of cash before completion.
8. Missing the costs that don't appear in the building contract
Land and construction are only part of the development budget.
A complete feasibility must also account for professional fees, surveys, engineering, approvals, authority contributions, certification, insurance, finance, holding expenses, legal costs, marketing and selling commissions.
GST and other tax considerations can also materially affect the project.
For example, the GST treatment of the acquisition and subsequent sales may influence the project's overall tax position and cash flow. Eligibility for the GST margin scheme should be assessed for the particular transaction rather than assumed.
Before you buy: Prepare a comprehensive development cost schedule and obtain project-specific accounting and legal advice on acquisition structure, GST treatment and relevant transaction costs.
Don't confuse a low building price with a low total development cost.
9. Underestimating builder, variation and contingency risks
A low tender price can make a feasibility look attractive.
But what happens if the builder has excluded essential work, allowed insufficient funds for subcontractors or cannot complete the project?
Builder selection and contract procurement are commercial risks that deserve attention before construction begins.
Developers should review tender qualifications, relevant experience, financial capacity, proposed personnel and the scope of works.
An appropriate contingency is also necessary to account for uncertainty and unforeseen costs.
However, contingency should not become a substitute for incomplete documentation or inadequate due diligence.
Before you buy: Identify significant construction risks, clarify exclusions and include a contingency that reflects the project's complexity and stage of design.
The goal is to reduce uncertainty before signing the building contract—not simply hope that the contingency will cover whatever goes wrong.
10. Only testing the numbers you want to see
This is the feasibility risk that can expose every other weakness in the project.
A developer prepares a spreadsheet using the expected construction cost, anticipated selling prices and preferred completion date.
The projected profit looks attractive.
But what happens when the assumptions change?
What if construction costs rise by 10%? Selling prices fall by 5%? Completion takes six months longer?
And what happens when several of those risks occur together?
How quickly can development profit disappear? (Tabe)
Consider this hypothetical project:
Feasibility item | Base case | Downside scenario |
Gross Realisation Value | $10,000,000 | $9,500,000 |
Total development costs | $8,000,000 | $8,800,000 |
Forecast development profit | $2,000,000 | $700,000 |
Profit on cost | 25% | 8.0% |
Illustrative figures only. The downside scenario assumes a 5% reduction in revenue and a 10% increase in total development costs, including the assumed financial impact of delays.
The project still shows a forecast profit, but its profit on cost has fallen from 25% to approximately 8%.
The developer is committing substantial capital and accepting construction, finance and market risk for a much smaller potential return.
This is why every serious property development feasibility should include sensitivity analysis and downside scenario testing.
Sensitivity analysis examines the effect of changing individual assumptions, such as construction costs, selling prices or interest rates.
Scenario analysis tests how several changes affect the project together.
Don't just ask how much profit your development could make. Ask how much risk it can absorb before that profit disappears.
Your Feasibility Should Evolve With The Development
A preliminary feasibility is designed to determine whether a site warrants further investigation. It will contain assumptions because detailed design, specialist reports, final construction pricing and confirmed finance terms may not yet be available.
That is acceptable—provided those assumptions are clearly identified.
As more information becomes available, the feasibility should be updated.
Before acquisition, test the development concept, indicative costs, revenue and funding requirements.
After due diligence, incorporate the findings of planning, engineering, survey and infrastructure investigations.
Before committing to construction, update the model using the coordinated design, construction pricing, programme and proposed finance terms.
During delivery, compare actual expenditure, variations, drawdowns and programme changes against the current feasibility.
A feasibility prepared before purchasing the land should not be the same spreadsheet you rely on when committing to construction twelve months later.
The numbers need to reflect the project as it exists today, not the project you originally imagined.
How OwnerDeveloper helps identify property development feasibility risks
At OwnerDeveloper, we approach development feasibility as a commercial decision-making process, not an exercise in producing an attractive profit figure.
Through our Development Management services, we help developers assess planning potential, coordinate professional advice, identify infrastructure and construction constraints, and test project costs against realistic market expectations.
We also consider the relationship between the development programme, finance structure, equity requirements and potential return.
As the project progresses, the feasibility can be updated with more reliable information to support decisions about design, procurement, funding and delivery.
The objective is to understand what can realistically be developed, what it will cost, what the market may pay and which risks could change the outcome.
Conclusion: Don't Buy the Profit. Test the Risk.
Every property development involves uncertainty.
Costs can increase. Approvals can take longer. Site investigations can reveal unexpected constraints. Market conditions can change before the completed properties are ready for sale.
A feasibility study cannot eliminate those risks.
What it can do is help you identify them early, understand their financial impact and decide whether the potential return justifies proceeding.
The biggest mistake is not necessarily getting one number wrong.
It's committing to a development without understanding how much the numbers can change before the project stops making commercial sense.
Before purchasing your next development site, speak with OwnerDeveloper about testing its feasibility, identifying critical risks and establishing whether the opportunity genuinely stacks up.
Frequently Asked Questions
What are the biggest feasibility risks in property development?
The main risks include overestimating development yield or sales revenue, underestimating construction and infrastructure costs, paying too much for land, miscalculating finance requirements and allowing unrealistic project timeframes. A thorough property development feasibility study identifies these risks before you commit substantial capital.
How can I tell if a property development is financially feasible?
Start by assessing what can realistically be built on the site, the likely completed sales value and the full cost of acquiring, approving, constructing, financing and selling the development. Then compare the forecast profit with the capital, time and risk involved. A project should also be tested against less favourable cost, revenue and timing assumptions.
What costs are commonly missed in a property development feasibility study?
Frequently overlooked costs include demolition, excavation, retaining walls, utility connections, authority contributions, consultant fees, finance charges, holding costs, GST, marketing, selling commissions and contingency allowances. These expenses can substantially reduce the profit shown in an early feasibility.
Why is sensitivity analysis important in property development?
Sensitivity analysis shows how changes to individual assumptions—such as higher construction costs, lower selling prices or increased interest rates—affect forecast profit. Testing combined downside scenarios helps developers understand whether a project remains commercially viable when several risks occur together.
When should I update my property development feasibility study?
Update your feasibility whenever new information could materially change the project's costs, revenue, programme or funding requirements. Key stages include completing site due diligence, refining the design, receiving construction tenders, confirming finance terms and monitoring costs during construction. A feasibility should remain a live decision-making tool throughout the development—not just a spreadsheet prepared before purchase.
#PropertyDevelopmentFeasibility #FeasibilityStudy #PropertyDevelopmentRisks #PropertyDevelopment #PropertyDevelopmentAustralia #DevelopmentFeasibility #DevelopmentRiskManagement #PropertyDeveloper #DevelopmentProfit #ConstructionCosts #DevelopmentFinance #PropertyInvestmentAustralia #PropertyDevelopmentCosts #PropertyDevelopmentDueDiligence #DevelopmentManagement #OwnerDeveloper
I found the downside scenario particularly interesting. Going from a 25% profit on cost to 8% shows how quickly a seemingly attractive deal can change.
The point about losing just one townhouse from the proposed yield really puts things into perspective. One planning or engineering constraint can completely change the numbers.