Development Math

The Full Cost Stack

Development math is the discipline that separates developers from speculators. A speculator buys land hoping it goes up. A developer buys land, runs a cost stack, projects revenue, stress-tests assumptions, and only proceeds if the margin justifies the risk and the timeline. The cost stack has six categories: land, horizontal development, vertical construction, soft costs, carry costs, and contingency. Miss any one of them and the project that looked profitable on a napkin becomes a money pit in reality. Every experienced developer has a story about the deal that looked great until they discovered the sewer line needed a $200K lift station, or the soil required $150K in remediation, or the county added $80K in impact fees after they closed on the land.

Land Cost and Horizontal Development

Land typically represents 20-30% of total project cost, though this varies enormously by market. In Manhattan, land can be 50%+ of total cost. In rural exurbs, land might be 10%. The raw land price is only the beginning. Horizontal development covers everything required to turn raw land into buildable lots: roads, curbs, gutters, sidewalks, water lines, sewer lines (or septic systems), storm drainage, electrical service, gas lines, and street lighting. For a 10-lot subdivision, horizontal costs typically run $15-40K per lot. A lot requiring a sewer lift station, significant rock removal, or a long road extension can push per-lot horizontal costs to $50-60K. Utility availability is the single biggest variable. If municipal water and sewer are at the property line, connection fees might be $5-10K per lot. If you need to extend water lines 1,000 feet to reach the property, that extension alone can cost $50-100K.

• Land: 20-30% of total project cost in most markets
• Roads and curbs: $20-50 per linear foot depending on width and specification
• Water and sewer lines: $30-80 per linear foot for installation
• Storm drainage: $10-30K per lot depending on topography and requirements
• Per-lot horizontal cost: $15-40K typical, $50-60K for difficult sites
• Utility availability check is step one of any land due diligence

Vertical Construction and Soft Costs

Vertical construction is the building itself. For residential, costs range from $150-300/SF depending on market, specification level, and builder efficiency. A 2,000 SF spec home at $175/SF costs $350K to build. A custom home at $250/SF costs $500K. Production builders achieve lower per-unit costs through repetition, bulk material purchasing, and standardized plans. Soft costs cover everything that is not physical construction: architectural and engineering fees ($8-25K), survey and geotechnical ($2-5K), legal fees ($5-15K for a subdivision), accounting, permit fees and impact fees ($5-30K per unit), marketing and sales commissions (5-7% of sale price), and insurance during construction. Soft costs typically run 15-20% of hard costs (horizontal + vertical). First-time developers consistently underestimate soft costs. Legal fees for a contested rezoning, engineering redesigns after plan review comments, and sales commissions on the finished product add up faster than expected.

• Vertical cost: $150-300/SF residential. Production builders at the low end, custom at the high end.
• Architecture and engineering: $8-25K depending on project size and complexity
• Legal: $5-15K for subdivision work, more for contested entitlements
• Permits and impact fees: $5-30K per unit
• Sales commissions: 5-7% of sale price at disposition
• Soft costs total: 15-20% of hard costs. Budget accordingly.

Carry Costs and Contingency

Carry costs are the ongoing expenses during the development period: interest on the construction loan, property taxes, builder's risk insurance, and general overhead (project management, administrative costs, site security). Construction loans typically carry rates of prime + 1-3%, which in recent years has meant 8-12% annually. On a $2M draw, that is $160-240K per year in interest. If the project takes 18 months instead of 12, you just added $80-120K in unplanned interest expense. Property taxes continue during construction, and in some jurisdictions the assessed value increases as improvements are added. Insurance costs $3-8K per year for a residential project, more for commercial. Contingency is your buffer for the unknown. Industry standard is 5-10% of hard costs. Experienced developers working in familiar markets and conditions can get away with 5%. First-time developers in unfamiliar territory should budget 10% or more. The contingency is not a slush fund. It exists because soil conditions surprise you, material prices shift, inspectors require changes, and weather causes delays.

• Construction loan rates: prime + 1-3% (8-12% recently)
• Interest on $2M draw: $160-240K/year
• Property taxes: continue during construction, may increase as value increases
• Builder's risk insurance: $3-8K/year residential, higher for commercial
• Contingency: 5-10% of hard costs. Not optional, not a luxury.
• Every month of delay adds carry cost and delays revenue. Double impact on returns.

Worked Example: 10-Lot Subdivision

A developer identifies a 10-acre agricultural parcel at the edge of a growing suburb. The land is priced at $500K. Municipal water and sewer are 500 feet from the property. The comprehensive plan shows this area as future residential. The developer plans to rezone, subdivide into 10 lots, build 10 spec homes at 1,800 SF each, and sell them at $450K apiece. The cost stack: Land $500K. Horizontal development (roads, utilities, grading, drainage) $300K ($30K per lot). Vertical construction $2M (10 homes at $200K each, $111/SF using a production builder). Soft costs $400K (architecture, engineering, legal, permits, impact fees, sales commissions). Carry costs $200K (18-month project, construction loan interest, taxes, insurance). Contingency $170K (roughly 6% of hard costs). Total investment: $3.57M. Revenue: 10 homes at $450K = $4.5M. Gross profit: $930K. Margin: 26%. That margin looks healthy. But if construction runs 6 months over schedule, carry costs increase by $100K, dropping profit to $830K and margin to 23%. If lumber spikes and adds $15K per home ($150K total), profit falls to $680K (19%). If both happen, profit is $580K (16%). The margin erodes fast when assumptions miss.

• Land: $500K (14% of total)
• Horizontal: $300K / $30K per lot (8%)
• Vertical: $2M / $200K per home (56%)
• Soft costs: $400K (11%)
• Carry: $200K (6%)
• Contingency: $170K (5%)
• Total: $3.57M. Revenue: $4.5M. Profit: $930K (26% margin).
• 6 months late + lumber spike = $580K profit (16% margin). Still profitable, but barely worth the risk.

Cost Stack Distribution: 10-Lot Subdivision

The chart below shows where the money goes in the worked example. Vertical construction dominates at 56% of total cost. This is typical for residential development. In commercial development, horizontal and soft costs represent a larger share because site work is more complex and regulatory requirements are heavier.

The development cost stack has six layers: land (20-30%), horizontal development ($15-40K per lot), vertical construction ($150-300/SF), soft costs (15-20% of hard costs), carry costs (a function of time and loan terms), and contingency (5-10% of hard costs). A 10-lot subdivision example shows a 26% margin under base assumptions, but that margin degrades to 16% if the project runs late and materials spike. Development math rewards precision and punishes optimism. Run the numbers conservatively, stress-test your assumptions, and never skip contingency.