Affordable Set Aside Impact Calculator

Set-aside affordable units reduce project NOI.

Total units

Set-aside %

Market rent per unit/yr

Affordable rent per unit/yr

Cap rate %

Value cost of set-aside

$4,909,091

Affordable units

Annual NOI gap

$270,000

How the math works

Affordable units = total × %. NOI gap = units × (market − affordable). Value cost = gap / cap.

180 × 15% = 27 affordable. × $10k gap = $270k NOI gap. / 5.5% = $4.9M value cost.

How to Use

Enter total units.
Enter set-aside %.
Enter market rent per unit.
Enter affordable rent per unit.
Enter cap rate.
Read value cost.

Frequently Asked Questions

Set-aside math?

Total units × set-aside % = affordable units. (Market rent − affordable rent) × affordable units = annual NOI gap. Divided by exit cap = value cost. Typical: 10-20% set-aside at 60-80% AMI affordable rents → 5-15% project value reduction.

Long-term burden?

Affordability restrictions run 15-55 years typically. Compounds with market rent growth: today's $200/mo gap becomes $400/mo in 15 years. Project discount reflects present value of multi-decade rent gap — model carefully for hold period.

Offsets?

Density bonus (extra market units). Property tax abatement. Reduced parking requirement. Expedited permitting. LIHTC equity (for larger affordable sets). Fee reductions. In many cases offsets fully monetize the set-aside cost; in others, net project cost.