Underwriting development risk and the pro forma

Land basis is the anchor. Overpay here and no amount of construction discipline saves you, because every downstream number is measured against a cost you already locked in. A useful rule of thumb professionals cite: land should be roughly 15% to 20% of total project cost for suburban multifamily, higher in dense urban markets. If land is 40% of your budget, the deal is fragile before you break ground.

Building the Cost Stack

Total development cost has three big buckets.

Hard costs. The physical build: concrete, framing, mechanical systems, finishes. For garden-style suburban multifamily in 2026, hard costs are commonly estimated in the range of $150 to $250 per square foot, though this varies widely by market and product type. This is your largest and most volatile line.

Soft costs. Everything not physical: architecture, engineering, legal, permits, insurance, and marketing. Typically 15% to 30% of hard costs.

Financing costs. Loan fees plus interest paid during construction, when the building earns nothing.

The Construction Draw

You do not pay the whole build at once. A construction loan funds through draws: periodic disbursements the lender releases as work is completed and inspected. A typical structure is a loan-to-cost (LTC) ratio, the share of total cost the lender will finance, often 60% to 70% for development in a cautious 2026 credit environment.

Here is the trap. Interest accrues on the drawn balance. The longer construction runs, the more months of interest you carry with zero rent coming in. This is why timing delays are not just annoying: they are a direct financial cost.

For a working introduction to how these budgets are assembled, the Urban Land Institute publishes accessible primers on development finance fundamentals.

Quantifying the Two Killers: Overruns and Delays

Two variables destroy more development deals than any market crash.

Cost Overruns

Assume a $50 million hard-cost budget. A 15% overrun is $7.5 million of unplanned spend. If your projected profit was $12 million, you just erased more than half of it with a single number that construction veterans will tell you is common, not extreme.

Developers protect against this with a contingency: a reserve line, usually 5% to 10% of hard costs, set aside for the unexpected. A deal with a 3% contingency in a volatile materials market is underwriting optimism, not risk.

Timing Delays

Delays hit three ways at once:

• Extra interest carry. More months of loan interest on the drawn balance.
• Delayed revenue. Rent starts later, pushing your whole income timeline right.
• Market drift. By the time you deliver, rents or cap rates may have moved against you.

A nine-month permitting delay on a large project can easily add seven figures in carry alone. Time is the one input a developer controls least and pays for most.

🎬 [VIDEO: "How to Build a Real Estate Development Pro Forma" — https://www.youtube.com/results?search_query=real+estate+development+pro+forma — a step-by-step walkthrough of building a development model from land to stabilization]

Lease-Up and the Revenue Side

Construction ends and the building sits empty. Now you must fill it.

Lease-up is the period from first move-in to stabilized occupancy, the point where the property hits a normalized occupancy level, commonly modeled at 93% to 95%. Lease-up takes time. A 200-unit project leasing at 15 to 20 units per month takes roughly ten to thirteen months to stabilize, and every one of those months carries expenses against partial income.

Two levers matter here:

• Achieved rents. Did you hit the rents in your pro forma? Underwriting $2,000 per unit and leasing at $1,850 is a 7.5% revenue miss that compounds across every unit, every year.
• Absorption pace. Slow lease-up means more months of carry and reserves burned.

The Metric That Separates Profit From Ruin: Yield on Cost

Here is the single most important number in development underwriting.

Yield on cost (YoC), also called development yield or return on cost, is your stabilized net operating income divided by total project cost.

Net operating income (NOI) is annual rental income minus operating expenses, before debt and taxes.

$$\text{Yield on Cost} = \frac{\text{Stabilized NOI}}{\text{Total Development Cost}}$$

Suppose stabilized NOI is $5.4 million and total cost is $72 million. Yield on cost is 7.5%.

The Spread That Pays You

Now compare yield on cost to the market cap rate: the yield an investor would accept to buy a finished, stabilized building. A cap rate is NOI divided by property value, so a lower cap rate means a higher price.

If similar stabilized buildings trade at a 5.5% cap rate, and you built to a 7.5% yield on cost, your development spread is 200 basis points (a basis point is one hundredth of a percent, so 200 bps equals 2%).

That spread is your profit margin for taking development risk. It works like this:

• Build to 7.5% yield on cost.
• Sell at a 5.5% cap rate.
• Your $5.4 million NOI, valued at 5.5%, is worth about $98 million, against your $72 million cost.

Developers generally want a spread of at least 150 to 200 bps to justify the risk versus simply buying an existing building. When cost overruns push yield on cost down toward the market cap rate, the spread vanishes, and with it the entire reason to develop.

Running the Whole Deal

Let us stack the phases into one picture.

| Line | Amount |

|---|---|

| Land basis | $6.0M |

| Hard costs | $50.0M |

| Soft costs | $12.0M |

| Financing costs | $4.0M |

| Total development cost | $72.0M |

| Stabilized NOI | $5.4M |

| Yield on cost | 7.5% |

| Value at 5.5% cap | $98.2M |

| Projected profit | ~$26M |

Now stress it. Apply a 15% hard-cost overrun ($7.5M) and a rent miss that cuts NOI to $5.0M:

• New total cost: $79.5M
• New yield on cost: 6.3%
• Value at 5.5% cap: $90.9M
• Profit: about $11.4M

The spread compressed from 200 bps to 80 bps. Profit fell by more than half. Push the overrun and delay further, or let cap rates rise to 6.5%, and the deal approaches breakeven. This sensitivity is the entire game.

Why Sensitivity Tables Matter

Sophisticated developers never present a single number. They model ranges: cost up 5%, 10%, 15%; lease-up slow by three months, six months; exit cap rate up 50 or 100 bps. The output is not one profit figure but a distribution of outcomes. Underwriting is asking, "How wrong can I be and still survive?"

Key Takeaways

• Land basis anchors everything. Overpaying for dirt cannot be fixed later. Keep land near 15% to 20% of total cost in suburban multifamily.
• Cost overruns and timing delays are the two primary killers. Carry adequate contingency (5% to 10%) and remember that every month of delay costs interest, revenue, and market risk simultaneously.
• Yield on cost versus market cap rate is the core metric. A development spread of at least 150 to 200 basis points is what compensates you for building instead of buying.
• Spread compression is silent and fast. A single overrun plus a modest rent miss can halve your profit without any dramatic market event.
• Underwrite ranges, not points. Stress-test cost, timing, rents, and exit cap rate together, and ask how wrong you can be and still make money.