Using Utah Internal ADU (IADU) and Mother-in-Law Basement Rent to Qualify for a Mortgage — Slickrock Skylight
Updated October 2026
A basement apartment can improve the economics of a Wasatch Front purchase, but projected rent and qualifying mortgage income are different numbers. Buyers in Salt Lake, Davis, Weber, and Utah counties frequently encounter internal accessory dwelling units, or IADUs. Whether that rent helps approval depends on the mortgage program, property classification, documentation, and lender requirements.
A listing that says “mother-in-law apartment” does not establish legal rental status or guarantee income credit.
Establish what the property actually contains
Start by asking the municipality about the unit’s permitted use and any applicable licensing, parking, safety, or owner-occupancy requirements. Then ask the lender how the appraiser must classify the property. A one-unit home with an accessory apartment is not automatically a legal duplex.
- Obtain available permits and documentation of lawful use.
- Identify separate entrances, kitchens, and living facilities.
- Ask whether an existing lease transfers with the purchase.
- Explain whether you intend long-term occupancy or short-term rentals.
These distinctions affect valuation and underwriting. They may also determine which loan limits apply, because a one-unit property with an ADU can remain a one-unit property for mortgage purposes.
Document income before counting it
Depending on the loan program, the lender may request a signed lease, market-rent appraisal support, evidence of rental receipts, tax returns, or landlord history. Some programs permit qualifying ADU income under specific restrictions; others handle proposed rent differently.
A common rental calculation recognizes only a portion of gross rent to account for vacancies and expenses. For illustration, 75% of $1,600 is $1,200. That example is not a promise that $1,200 will count: the applicable program can impose additional limits or require different treatment.
Review program information through HUD FHA Mortgage Limits and compare application documents using the Consumer Financial Protection Bureau. Ask for the qualifying-income calculation before removing a financing contingency.
The Utah mortgage options guide helps frame the program comparison, including conventional, FHA, and VA financing.
Budget for ownership without perfect occupancy
Run the monthly payment calculator both with and without rent. Allow for utilities, repairs, tenant turnover, insurance changes, and reserves. Rent that helps approval is still income you must collect and manage.
Utah primary residential tax treatment also deserves attention. A qualifying long-term residential use can differ from a short-term rental arrangement, and mixed-use details matter. Read the primary residential exemption guide and confirm the parcel’s treatment with the county rather than assuming every basement rental receives identical treatment.
Compare Current Mortgage Rates
Compare current APRs, points, fees, and estimated monthly payments from participating lenders below.
Loan Program Comparison: 2026 Benchmarks
Using Utah Internal ADU (IADU) and Mother in Law Basement Rent to Qualify for a Mortgage — Choose a mortgage by comparing eligibility, upfront cash and total monthly costs, not the advertised rate alone. Conventional, FHA, VA and USDA serve different borrowers. Confirm county limits, taxes, insurance and lender requirements before comparing personalized Loan Estimates for your household.
Historical 2025 one-unit comparison: conforming $832,750; FHA floor $541,287. County and unit-count limits can differ.
| Loan program | Down payment / equity | 2026 one-unit baseline | Costs and page-specific comparison |
|---|---|---|---|
| Conventional | 3%–5% subject to eligibility | $832,750 | PMI generally below 20% down |
| FHA | 3.5% at 580+; 10% at 500–579 | $541,287 floor | 1.75% upfront MIP; 0.55% annual for >95% LTV, base loan ≤$726,200, term >15 years |
| VA | 0% for eligible borrowers | No VA limit with full entitlement | No monthly PMI; funding fee unless exempt |
| USDA | 0% for eligible borrowers | Income, address and repayment eligibility | Guarantee and annual fees; confirm current schedule |
| Jumbo | Lender-specific cash and reserves | Above applicable conforming limit | Lender-specific pricing and insurance |
| Home Equity / Refinance | Equity and underwriting dependent | Property and lender dependent | Compare closing costs, term and break-even |
Sources: FHFA limits; HUD FHA limits.
Editorial Methodology & Primary Sources
Verification date: Not recorded; check the primary source and lender timestamp before relying on an estimate.
Rate comparisons use participating lender feeds, not a whole-market survey or guaranteed offers. Freddie Mac PMMS is a market benchmark, not a personalized quote. Calculator models rely on published regulatory formulas and disclosed assumptions rather than fabricated first-person loan testing.
Monthly principal and interest use the amortization formula P × r / (1 − (1 + r)−n), where r is the monthly note rate and n is the number of payments; at zero interest use P / n. PITI adds monthly property taxes and homeowners insurance; PMI is separate. APR includes applicable finance charges under Regulation Z and is not the note rate used for payments. Compare lender Loan Estimates for actual APR and fees.
- Consumer Financial Protection Bureau (CFPB) — Loan Estimates, APR and borrower disclosures; Regulation Z.
- U.S. Department of Housing and Urban Development (HUD / FHA) — FHA program guidance.
- U.S. Department of Veterans Affairs (VA) — VA loan eligibility and benefits.
- Freddie Mac Primary Mortgage Market Survey (PMMS) — published rate benchmarks.
- U.S. Census state tax collections — state property tax benchmarks; confirm parcel-specific assessments and exemptions with the state revenue department and local assessor.
- Utah Housing Corporation — state housing finance and property tax authority.
- Utah State Tax Commission Property Tax — state housing finance and property tax authority.
The payment snapshot uses illustrative annual taxes of 1% of home price, $1,200 insurance and 0.5% PMI below 20% down, not verified local quotes. Other calculators disclose their inputs and assumptions. Published guidance and lender feeds may change independently; confirm current program rules, taxes and offers before a decision.