Under Fannie Mae’s DU 12.1 update, live the weekend of March 21, 2026, projected ADU rental income can’t be used to qualify on a full cash-out refinance. Freddie Mac’s Guide Section 5306 takes the same position: rental income from an accessory dwelling unit counts only on purchase and no-cash-out (rate-and-term) refinances. And that single rule reshapes almost every homeowner plan to “just refi and let the ADU pay for itself.” The build can still be funded with cash-out proceeds. But qualifying income on the same loan? That’s another matter.
The rule most ADU-planning homeowners get wrong
Fannie Mae permits ADU rental income for qualifying, capped at 30% of total qualifying income and counted from only one ADU per one-unit principal residence. Freddie Mac allows 75% of gross monthly rent from a lease, or 75% of market rent from the ADU rental analysis when no lease exists (subject to the same 30% cap). In both cases, transaction type is the gate. Full cash-out is out. Limited cash-out (Fannie) and no-cash-out (Freddie) are in.
So why does the label distinction matter? Because most homeowners hear “refinance” and treat all three products as interchangeable. They’re not. A full cash-out refinance takes cash beyond limited allowances for closing costs and paying off certain non-mortgage debt. A limited cash-out refinance pays off the existing lien plus closing costs and permits a small cash payment – up to 2% of the new loan balance or $2,000, whichever is less, per Fannie’s Selling Guide. If the goal is to pull tens of thousands of dollars to fund an ADU build, the loan is a full cash-out. Projected rent can’t help.
How the equity math actually runs
Conventional cash-out refinance on a 1-unit primary residence is generally capped at 80% LTV. The borrower retains at least 20% equity after taking cash out. Investment properties sit lower, typically 70% to 75% LTV. For 2026, the baseline conforming loan limit is $806,500 for one-unit properties, with a high-cost county ceiling of $1,209,750. Loans above those thresholds move into jumbo underwriting, where cash-out ceilings and reserve requirements tighten further.
Work the math. On a $600,000 home carrying a $250,000 first mortgage, 80% LTV supports a new loan of $480,000. After paying off the existing $250,000 and roughly $10,000 in closing costs and cash-out pricing adjustments, the borrower nets about $220,000 in proceeds. That covers a mid-range detached ADU or a fully finished garage conversion. But it doesn’t cover a $300,000 detached build without a second funding source or a lower-cost scope.
Cash-out pricing adjustments (LLPAs) hit hardest at higher LTVs and lower credit scores. A 780 FICO borrower at 70% LTV faces a small hit. A 700 FICO borrower at 80% LTV can see the price adjustment cost multiple points – which the lender either bakes into the rate or collects at closing.
The appraisal is as-is, not subject-to-completion
Standard cash-out refinances appraise the property as-is on the date of inspection. The future ADU isn’t in the number. A homeowner counting on the post-build value to unlock proceeds will come up short at the closing table. And this is the second most common misread of the product, right after the rental-income rule.
Fannie Mae and Freddie Mac begin mandatory use of the UAD 3.6 appraisal framework on November 2, 2026, which expands ADU-specific reporting fields. UAD 3.6 changes how appraisers document existing ADUs. But it doesn’t convert a standard cash-out appraisal into a subject-to-completion appraisal for a unit that hasn’t been built yet.
Homeowners who need the post-build value baked into the loan should look at HomeStyle Renovation (Fannie), CHOICERenovation (Freddie), or a construction-to-permanent structure. Those products underwrite to as-completed value using plans, specs, and a lender-approved contractor bid. A plain cash-out doesn’t.
Qualifying on the new payment, without ADU rent
Full-cash-out qualifying runs on the new, larger first-mortgage payment and the borrower’s documented income. Debt-to-income ceilings on conventional cash-out generally cap in the mid-40s, with the exact ceiling driven by AUS findings, reserves, and credit tier. So if the borrower’s DTI only clears with the ADU rental income added in, the loan doesn’t close as a full cash-out. Experienced loan officers run the DTI without the phantom rent before they ever open the ADU conversation with a homeowner, not after underwriting sends the file back with conditions.
Two workable pivots exist. Restructure to a HELOC or fixed-rate HELOAN as a second lien and leave the first mortgage in place. Or wait until the ADU is built and leased, then refinance as a limited cash-out or rate-and-term where the rent can count toward qualifying income.
Reserves matter too. Cash-out on a primary residence typically requires two to six months of PITIA in reserves after closing (depending on loan size, LTV, and credit score). Borrowers planning to spend most of their liquid savings on the build itself should model this before locking, not after.
When cash-out refi is the wrong instrument
Anyone holding a first mortgage at 3% to 4% should think twice. Replacing that lien with a 2026-rate cash-out means every dollar of the old balance reprices. On a $250,000 balance, moving from a 3.25% rate to a rate several points higher can add hundreds of dollars per month, most of it going to interest rather than the ADU. But a second-lien HELOC or HELOAN preserves the low-rate first mortgage and applies the higher rate only to the drawn balance. Run the break-even math before assuming cash-out is the cheaper route.
Detached ground-up builds with thin equity? The other frequent misfit. If the current-state appraisal can’t support 80% LTV proceeds equal to the build cost, cash-out can’t bridge the gap. Renovation refi or construction-to-permanent underwrites to the completed project and closes that gap instead.
And borrowers who planned to lean on projected ADU rent to clear DTI can’t use a full cash-out. Freddie Mac and Fannie Mae are explicit on this point in the 2026 guides.
Decision matrix: product against build type
| Product | Best when | Weakest when |
|---|---|---|
| Cash-out refi (first lien) | Existing rate at or above current cash-out rate; 20%+ equity; wants one loan | Sub-4% legacy first mortgage; needs post-build value; ADU rent needed to qualify |
| HELOC (second lien) | Legacy first mortgage worth keeping; phased contractor draws | Variable-rate exposure; end-of-draw payment shock |
| HELOAN (fixed second) | Wants payment certainty and keeps first mortgage | Rate typically higher than a first-lien cash-out |
| FHA 203(k) | Attached ADU or rehab-into-ADU scope | Detached standalone ADU; program complexity |
| HomeStyle / CHOICERenovation | Needs as-completed value; wants one closing | Not every lender offers for ADU scope |
| Construction-to-permanent | Larger detached builds; needs post-build value in the loan | More draws, more inspections, complex closing |
Region matters, especially in California
California preempts local zoning on ADUs on most single-family lots. AB 1033 additionally permits jurisdictions to opt in to letting ADUs be sold separately as condominium units. San Diego County adopted AB 1033 effective April 4, 2026. Financing doesn’t change based on state ADU law. But feasibility does. A California build usually clears permitting. A build in a jurisdiction that hasn’t adopted state-level preemption may not. The California ADU grant program has previously offered up to $40,000 for qualifying homeowners, though funding cycles have run out in past rounds (worth checking current program status before counting on it).
Outside California, Oregon, Washington, Colorado, Massachusetts, and Vermont have adopted broader ADU-permissive frameworks. Reports on the total number of states allowing ADUs by right vary, and they should be checked against a primary source before repeating.
A five-step path from equity to keys
The route from equity to a finished ADU walks through five checks, and most of them fit into an afternoon of desk work. Start by pulling a current-state comparative market analysis to estimate the as-is appraised value, then model the 80% LTV cash-out ceiling against total build cost with a 10% to 15% contingency baked in (and never skip the contingency, because a build always finds a way to spend it). Run DTI on the new, larger first mortgage with zero credit for future ADU rent – if it doesn’t clear, no full cash-out will. Next, request quotes on both a cash-out refi and a HELOC or HELOAN from the same lender, then compare total cost of borrowing over the build horizon rather than the headline rate. Finally, choose the product that survives the math, lock the rate, and structure the draw or lump sum around the contractor’s payment schedule.
Requirements vary by lender. Confirm current LTV caps, cash-out pricing adjustments, and reserve requirements with a Fannie- or Freddie-approved lender, and pull the ADU rental-income posture in writing before assuming any rent will count toward qualifying.
Frequently asked questions
Can I use future rent from an ADU to qualify for a cash-out refinance?
No. On a full cash-out refinance, both Fannie Mae (DU 12.1) and Freddie Mac (Guide 5306) prohibit using projected ADU rental income for qualifying. Rent counts only on purchase and no-cash-out or rate-and-term refinances, and only up to 30% of qualifying income.
Does the appraisal include the ADU I’m about to build?
No. A standard cash-out refi values the home as-is on the date of inspection. If you need post-build value in the loan, the product has to be HomeStyle Renovation, CHOICERenovation, or construction-to-permanent.
Is a cash-out refinance or a HELOC better for building an ADU?
It depends on the existing rate. A cash-out refi replaces the entire first mortgage, so borrowers holding a sub-4% legacy rate usually pay more in total interest than they would with a HELOC or HELOAN that leaves the first lien in place. Cash-out generally wins only when the existing rate is close to or above current cash-out rates.
How much equity do I need for an ADU cash-out refinance?
Enough to keep the new first-mortgage balance at or below 80% of the home’s current appraised value. On a $600,000 home with a $250,000 first mortgage, that caps cash-out proceeds at roughly $220,000 after closing costs.
What’s the difference between a full cash-out and a limited cash-out refinance?
A limited cash-out (Fannie) or no-cash-out (Freddie) refinance pays off the existing lien plus closing costs and returns only a small cash amount to the borrower. A full cash-out takes cash beyond that threshold and gets priced and underwritten more conservatively as a result.
Can I use an FHA 203(k) loan to build a detached ADU?
Usually not. FHA 203(k) is built for rehab work on the existing structure and attached additions. Detached ground-up ADU builds typically fall outside its scope. Confirm current Handbook 4000.1 treatment with an FHA-approved lender before assuming eligibility.
Can I refinance while my ADU is under construction?
Not with a standard cash-out. Lenders won’t fund a first-lien refinance on a property with active construction. Construction-to-permanent products handle the build phase and convert to permanent financing at completion.
