How to test development cost and completed value
An early property study is useful when every result can be traced to a source or an editable assumption. A precise dollar figure without that distinction can be misleading.
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1. Start with the design quantity
Confirm a conditional program: number of units, ground footprint, floors, gross floor area and saleable or rentable area. The 2D and 3D views should represent the same saved geometry. Net area is smaller than gross area because circulation, walls and shared space consume floor area. Parking drawn in a concept needs its own access and compliance review.
If the parcel boundary or applicable zoning is uncertain, keep the design conditional. Do not convert a massing diagram into a claim of permitted homes or a permit-ready floor plan.
2. Build an itemized planning budget
For illustration, assume 10,000 gross sq ft at $250 per gross sq ft: $2.5 million in base building cost. Add soft costs of 15% of that base ($375,000), a 10% contingency ($250,000), and a $300,000 site-work allowance. The illustrative subtotal is $3.425 million. These numbers are teaching assumptions, not a local quote.
Acquisition, demolition, permitting, utilities, unusual foundations, financing, carrying costs and taxes may sit outside this simplified subtotal. If a line is unpriced, show it as unpriced rather than silently treating it as zero. Project-specific bids and agency fee schedules should replace allowances before commitment.
3. Keep gross value separate from return
Assume 8,000 saleable sq ft at an illustrative $500 per saleable sq ft. Gross completed sale value is $4 million. At 5% selling costs ($200,000), subtracting the $3.425 million subtotal leaves $375,000 before land acquisition and the excluded costs above. That is not profit, net proceeds or an investment return.
For a rental strategy, an income value requires supported stabilized net operating income and a defensible capitalization rate. Asking rent, tax assessment and an old sale price are different observations; none should automatically become today’s property market value.
Stress-test the same teaching case
The table uses the same fictional 10,000 gross sq ft building, 8,000 saleable sq ft and $300,000 site allowance described above. Soft costs remain 15% of base building cost; contingency remains 10%. Selling costs remain 5% of gross sale value. No market data or actual property is represented.
When the building rate rises, the two percentage-based allowances rise with it. The site allowance stays fixed in this deliberately limited test. A real project needs a separate review of site costs, timing and financing.
| Assumed change | Budget subtotal | Gross sale value | Balance before excluded costs |
|---|---|---|---|
| Teaching case | $3,425,000 | $4,000,000 | $375,000 |
| Building rate +10% | $3,737,500 | $4,000,000 | $62,500 |
| Sale price −10% | $3,425,000 | $3,600,000 | −$5,000 |
| Both changes | $3,737,500 | $3,600,000 | −$317,500 |
Read the result before calling it a return
In the teaching case, $375,000 is all that remains for acquisition and the excluded costs—not profit. A 10% sale-price reduction consumes that entire amount and leaves a $5,000 shortfall before buying the land. Combining the lower price with the higher building rate leaves a $317,500 shortfall before those same exclusions.
This is why a positive difference between gross sale value and construction cost is not an investment decision. Include acquisition, closing, demolition, permits, utilities, taxes, insurance, financing and holding costs. Check the scope of each quote so an allowance is neither omitted nor counted twice. If a required amount is unknown, leave dependent returns unavailable.
Keep the measurement basis with every price
A price needs both an area or unit basis and a time period. $30 per sq ft per year is $2.50 per sq ft per month before any other lease terms; it is not $30 per unit per month. Keep commercial, office and residential income lines separate when their unit sizes or lease terms differ.
Building cost may be quoted per gross square foot while sale pricing refers to saleable area. In this example, pricing all 10,000 gross sq ft at $500 would overstate gross sale value by $1 million compared with the stated 8,000 saleable sq ft. That is a measurement error, not a market upside.
Replace assumptions with evidence in the right order
Start with the quantities and permission limits, then obtain scope-specific cost quotes. For a sale strategy, record relevant closed-sale evidence and any adjustments. For a rental strategy, record the unit mix, supported rent basis, vacancy, operating expenses and capitalization-rate rationale separately. A neighborhood index is context, not a lease offer for a particular unit.
Save the source, observation period and date checked for every replacement. Rerun the complete case when a design quantity or price changes. A worksheet organizes these inputs; it does not calculate a property approval, appraisal or investment return.