Portland ADU rental income for mortgage qualifying
Oregon's SB 1537 (effective 2025) makes ADU permitting easier across Portland metro and statewide. For buyers, that means more properties qualify with rentable accessory dwellings — and that rental income can boost mortgage qualifying power.
What SB 1537 changed
Oregon has required cities to allow ADUs by right since SB 1051 (2017), and the state's newer housing package — SB 1537 (2024) — keeps expanding options, including model codes that allow up to two ADUs per lot in urban growth areas. Removes most local barriers (lot size minimums, parking requirements, owner-occupancy mandates).
Result: Portland-metro properties with detached ADUs, converted garages, or basement apartments are far easier to permit and validate as legal rentals. Mortgage underwriting treats legally permitted ADUs as standard — the permit record is what underwriters verify.
How underwriting counts ADU income
Existing ADU with a current lease: typically 75% of documented rent counts toward qualifying on conventional loans — exact treatment varies by loan type and current agency rules. Documentation commonly includes a signed lease, bank deposits showing rent received, and the ADU on the tax return — the lender applies the current investor and agency documentation rules for your specific loan type and whether it's a purchase or refinance.
Vacant ADU with rental potential: order Form 1007 (Comparable Rent Schedule) at appraisal. Appraiser estimates fair market rent. typically 75% of that estimate can count toward qualifying income, depending on loan type and current agency rules.
Portland scenario — buying a SE Portland Craftsman with backyard ADU
| Item | Without ADU income | With ADU income |
|---|---|---|
| Buyer's W-2 income | $96K | $96K |
| ADU monthly rent (75% counted) | $0 | $1,425 ($1,900 × 75%) |
| Annualized qualifying income | $96K | $113,100 |
| Effect on buying power | Baseline | Meaningfully higher — exact amount depends on debts, taxes, insurance, and current qualifying terms (illustrative only) |
Common questions
Does the ADU need to be detached or can it be a basement apartment?
Either works for qualifying purposes. Legal permitting is what matters — make sure the city has the ADU on record.
Can I use short-term rental (Airbnb) projections?
Not for conventional, FHA, or VA. STR projections count on DSCR loans. Traditional mortgage qualifying needs long-term lease or appraiser rental schedule.
What if the seller has been renting the ADU under the table?
Income won't count unless documented. You'd need a new lease and documented income post-close, then refinance in the future to qualify with the income.
How do ADUs affect property taxes in Oregon?
ADUs typically increase property tax assessment. Plan for the increased escrow when modeling affordability.
How Mike + Cornerstone help
I'm licensed in Oregon. Portland-metro buyers benefit hugely from SB 1537 — properties with ADUs are now more common and easier to qualify on. We'll structure your file to capture every dollar of legal ADU income that can boost your buying power.
Talk to Mike first Get pre-approved
No pressure, no commitment. Free 20-minute consult. Mike will look at your scenario and tell you straight whether this works for you.