Age-Restricted MHP Underwriting: The 80% Occupancy Test

Published November 12, 2026

A 55-and-older park with 108 occupied lots needs at least 87 of those lots occupied by someone aged 55 or older. That is not a house rule the seller wrote. Section 100.305(a) of Title 24 of the Code of Federal Regulations sets the threshold at 80% of occupied units, and subsection (g) rounds a fractional unit up into the group that has to qualify, so 80% of 108 is 87 rather than 86. Subsection (c) measures the test on the date the exemption is claimed, not averaged across a year.

Miss it and the restriction stops being an exemption. The only thing that permits a Mobile Home Park (MHP) to turn families away on the basis of age is the housing-for-older-persons exemption at 42 U.S.C. 3607(b)(2)(C), as amended by the Housing for Older Persons Act of 1995. Without it, the same policy generally reads as familial-status discrimination under the Fair Housing Act. Requirements vary by state, so the local overlay is worth confirming with counsel.

Most offering memoranda treat the restriction as a selling point — low turnover, stable collections — and then drop it from the model. Age-restricted MHP underwriting treats it as what it is: a dated compliance covenant with a verification file behind it and a ceiling on the applicant pool that fills vacant lots.

Why Age-Restricted MHP Underwriting Starts With the 80% Test

The denominator is the part that gets missed. Section 100.305(a) measures 80% of occupied units, and subsection (e)(2) confirms that unoccupied units do not count against the community as long as 80% of the occupied ones qualify. A park with 12 empty lots is therefore tested on the 108 that are occupied, which means every lot leased changes the arithmetic. A vacancy campaign and a compliance ratio generally move in opposite directions.

Three other provisions carry weight in diligence:

• Temporarily vacant lots still count. Under 100.305(b)(2), a unit whose primary occupant has resided there during the past year and intends to return is treated as occupied, and under (c) it qualifies if an occupant immediately before the vacancy was 55 or older. Seasonal residents do not break the ratio.
• Staff and accommodation lots are carved out. Subsection (e)(3) allows units housing under-55 employees who perform substantial management or maintenance duties, and (e)(4) allows units occupied by people needed as a reasonable accommodation under Section 100.204.
• The cure runs forward only. Subsection (f) bars a community from evicting families with children, refusing to renew their leases, or otherwise penalizing them in order to reach the 80% figure. A ratio that has drifted below the line can generally only be repaired through the next lease signed.

That last point is the one that belongs in the model. The compliance ratio is an inventory that refills at the speed of resident turnover, and in age-restricted parks turnover tends to be low. The same quality that makes the asset attractive slows the only repair available.

What the Verification File Has to Contain

The exemption is not self-proving. Section 100.306(a) requires the community to publish and adhere to policies and procedures demonstrating the intent to operate as 55-or-older housing, and lists the factors the Department of Housing and Urban Development weighs: how the property is described to prospective residents, advertising, lease provisions, written rules and recorded restrictions, consistent application of those procedures, actual practice at the property, and public posting in common areas. Subsection (b) is specific about language — "adult living" or "adult community" in an advertisement or prospectus is treated as inconsistent with that intent, so an older park's own signage can argue against it.

Section 100.307 sets the evidence standard. The community needs routine procedures for determining the occupancy of each unit, and the occupancy information has to be updated through a survey or other means at least once every two years. Reliable proof includes a driver's license, birth certificate, passport, immigration card or military identification, or another official document with a comparably reliable date of birth; a certification signed by any household member aged 18 or older stating that at least one occupant is 55 or older is also acceptable. Where occupants refuse to comply, the community may still treat a unit as qualifying on sufficient evidence, including a sworn statement from someone with personal knowledge signed under penalty of perjury. A summary of the occupancy surveys has to be available for inspection by any person on reasonable notice.

In diligence that converts to four requests: the published policy, the current survey with its date, the age-documentation file keyed to the rent roll, and the advertising the park is actually running. A park that cannot produce a survey is not necessarily out of compliance, but it has no admissible proof of its ratio, which is a different and worse thing to inherit. Evidence standards vary by jurisdiction.

The Infill Plan Is Where the 80% Test Bites

Take an illustrative 120-lot age-restricted park: 108 lots occupied, 90 of those with at least one occupant aged 55 or older, 12 vacant lots, and lot rent of roughly $425 a month. Compliance today is adequate rather than generous: 80% of 108 is 86.4, rounded to 87 under 100.305(g), so the headroom is three lots.

Now run the infill plan, which is the core value-add lever and the subject of the lot-by-lot yield-on-cost work.

Figures are illustrative. Each lot filled by an under-55 household raises the requirement by 0.8 of a lot while leaving the qualifying count flat, so headroom erodes at roughly four-fifths of a lot per lease. Filling all 12 vacancies without an age screen puts the park six lots short of its own exemption. Holding the line requires at least six of the 12 to go to households with a 55-or-older occupant, and prudence argues for more, because the ratio also moves when a qualifying resident leaves.

The cost lands in timing rather than in rent. A park leasing one lot at the start of each month captures 78 lot-months of revenue in year one (12 + 11 + … + 1). A 55-or-older-weighted pipeline signing one lease every other month, in months 1, 3, 5, 7, 9 and 11, captures 42 (12 + 10 + 8 + 6 + 4 + 2), and fills only six of the 12 vacancies by year-end. At $425 a lot that is about $33,000 against about $18,000, a gap of roughly $15,000 of lot revenue, or roughly $10,000 of Net Operating Income (NOI) after a marginal expense load of about 35% for utilities, trash and collections on the new lots. None of it appears as a rent variance. It appears as a slower curve against the same capital plan, which is the same failure the economic occupancy work finds in a different line.

What the Compliance File Costs, and What Its Absence Risks

Standing up the Section 100.306 and 100.307 apparatus at a park that has been running on habit is a real line item, and it is almost never in the seller's trailing statements. On a park of this size an illustrative budget runs $6,000 to $9,000 in year one for counsel review of the policy and lease language, a mailed age survey reconciled to the rent roll, and a records system that can produce the summary on request, then roughly $2,000 to $3,000 a year to keep the survey inside the two-year window. These are illustrative estimates rather than sourced figures, and counsel and survey costs vary by market. The year-one setup reads best as a one-time closing cost added to the basis; the recurring piece, about $2,500 a year, is the part that belongs in NOI. It is small, and small is why it gets left out.

The contingent side is harder, and converting it to a cap rate would be false precision. If the exemption fails, the park has been turning families away on the basis of age without the statutory cover for doing so, and the exposure is a Fair Housing Act matter rather than an expense line. The treatment that holds up is a representation, a holdback sized to counsel's read, and a closing condition that the survey exists — not a basis-point adjustment. Exposure varies with the park's history and its state, so it is worth pricing with counsel on the specific asset.

Where the Agency Occupancy Gate and the 80% Test Pull Apart

Agency underwriting has its own occupancy test, and it is not this one. Freddie Mac's Multifamily Seller/Servicer Guide Section 22.2(e) requires a Manufactured Housing Community (MHC) to have demonstrated stabilized occupancy for not fewer than three consecutive months before loan closing, with stabilized occupancy generally defined as at least 85% of the Home Sites. The illustrative park above sits near 90% occupied and clears it. A park at 100 of 120 lots sits near 83% and does not, and the quickest route to 85% is to lease whoever applies, which is the one move the 80% test does not allow.

That is the collision worth modeling. Below the agency occupancy floor the park needs lots leased quickly; under the exemption it needs them leased selectively. The gap tends to get paid for in time, as a closing date that waits on a thinner applicant flow, or in structure, as bridge debt carrying the park to agency eligibility — whose proceeds consequence is the subject of the coverage-constrained debt work.

The restriction narrows the valuation evidence as well. Section 22.5(a) requires the appraiser to be knowledgeable about age-restricted MHCs, and 22.5(b)(1) asks that comparables be similarly classified, including whether a community is age-restricted. Fannie Mae's Multifamily Guide carries Age-Restricted MH Community as a defined term, describing a community that limits residents to those over a particular age and giving as examples persons aged 62 or older, or at least 80% of the homes occupied by at least one person aged 55 or older, so the restriction is a disclosed attribute of the collateral rather than an operating detail. Guide language changes, so current terms are worth verifying directly with the lender.

Sized at the margin, a combined year-one NOI gap of roughly $12,400 — about $9,900 of slower absorption plus about $2,500 of recurring compliance administration — is about $190,000 of value at a 6.5% cap rate, before the one-time setup cost. Against debt it is tighter. At a 1.25x Debt Service Coverage Ratio (DSCR) floor and an illustrative 7.6% debt constant, roughly a 6.5% coupon on 30-year amortization with the 10-year Treasury at 4.84% per the Federal Reserve's H.15 release for November 5, 2026, that $12,400 supports about $10,000 of debt service and roughly $130,000 of proceeds. Rate quotes move daily, and spreads on age-restricted MHC collateral vary by lender.

Where This Breaks

The constraint often does not bind. A park that has been age-restricted for decades usually sits well above 80%, because the resident base self-selects, and headroom of 15 or 20 lots makes this a diligence checkbox rather than a model input. The three-lot headroom above was chosen because it is the case that matters, not because it is the common one.

The absorption penalty also assumes the 55-or-older applicant pool is thinner than the general one, and in a retirement-destination submarket the opposite may hold. The demographic direction supports that reading: per the Census Bureau's August 31, 2026 release on older-adult population projections, 18.9% of U.S. residents were 65 or older in 2025, projected at 23.4% by 2060. A park sitting in that demand may lease age-restricted lots faster than open ones.

Low turnover cuts both ways. It protects collections and it starves the mark-to-market path, because rent generally resets on turnover, so a park with very little of it has a smoother income stream and a slower rent trajectory. And the compliance exposure resists quantification; no cap rate converts a contingent fair-housing claim honestly, which is why the treatment above is a holdback rather than a haircut.

The federal rule is also a floor rather than the whole test. State and local age-restriction law, including the notice and park-rule statutes of the kind covered in the rent regulation work, can be stricter, and an exemption that satisfies Section 100.305 can still fail a state standard. The lot-level mechanics sit in the MHP due diligence checklist, and the broader model in the mobile home park underwriting primer.

The Underwriting Takeaway

Age-restricted MHP underwriting resolves to one small table: occupied lots, lots with a qualifying occupant, the 80% requirement rounded up, and the headroom between them, pulled from the rent roll rather than the offering summary. Three tests tend to travel from it. Count the ratio before pricing the infill, because vacant lots are only worth the pro forma if households that can legally fill them exist in the submarket. Ask for the survey and its date, since the exemption is evidentiary and a compliant park without a survey still has no proof. And read the agency occupancy floor against the compliance ratio in the same pass, because a park below Freddie Mac's generally stated 85% of Home Sites and near 80% on age is being asked to lease quickly and selectively at the same time.

The sign at the entrance is a marketing asset. The ratio behind it is a covenant.

UWmatic is an AI-powered underwriting platform built for multifamily and mobile home park investors. Model the age-restricted lots as a separate absorption pool with its own pace, and see what a compliance-constrained infill plan does to year-one coverage. Try the free underwriting calculator →

This analysis reflects current market interpretations as of the publication date and may evolve as new data becomes available. Figures cited are drawn from public sources including Title 24 of the Code of Federal Regulations Part 100 Subpart E, the Housing for Older Persons Act of 1995 at 42 U.S.C. 3607(b)(2)(C), Freddie Mac's Multifamily Seller/Servicer Guide Chapter 22, Fannie Mae's Multifamily Guide, the U.S. Census Bureau's older-adult population projections, and the Federal Reserve's H.15 selected interest rates release, and are subject to revision. Nothing in this post is investment advice; readers should conduct their own diligence and consult qualified professionals before making investment decisions.