How do people pay for an ADU?

What are the main ways to pay for an ADU?

Most homeowners use savings, a loan against the equity in their home, or a renovation mortgage that lends on what the property will be worth once the accessory dwelling unit (ADU) is built. Equity is the share of your home you own outright: its value minus what you still owe. Many people combine sources.

Rates move daily. Those below are national averages from September 30 and October 1, 2026; yours will depend on your credit, equity, lender and loan size. Build an all-in budget first with our cost guide.

Should you use savings or your home’s equity?

Cash. Paying cash skips interest, appraisals and loan paperwork. The risk is leaving yourself no cushion if the project runs over or the furnace dies.

HELOC. A home equity line of credit (HELOC) works like a credit card backed by your house. You draw money as bills come due and pay interest only on what you’ve drawn, and your first mortgage stays as it is. The catches (CFPB, 2022):

• Most HELOC rates float, so payments can rise even after you stop borrowing.
• The lender can generally freeze or cut the line if your home’s value drops or your finances weaken. Mid-build, that could leave you with half an ADU.
• Some contracts limit renting out your home. Read yours before you plan to rent the ADU.
• Federal law gives you three days to cancel a new HELOC and get your fees back.

Home equity loan. Same collateral, but one lump sum at a fixed rate with a set payment. That suits a fixed-price contract, though you pay interest on money that sits waiting for the next stage of work.

Cash-out refinance. You swap your mortgage for a bigger one and take the difference in cash. The new rate applies to everything you owe, not just the new money. If your current rate is well below today’s, that can cost more each month than adding a HELOC or home equity loan, so ask a lender to price both. It also stops FHA, Fannie Mae and Freddie Mac from counting ADU rent toward qualifying (HUD, 2023; see the rent rules below).

With a HELOC, home equity loan or refinance, your home is the collateral, so missed payments could cost you the house (CFPB, 2022).

What if you don’t have much equity yet?

A renovation mortgage lends on the property’s “as-completed” value: what an appraiser expects it to be worth once the ADU is built, judged from your plans and contract. The lender holds the renovation money and pays the contractor in stages, called draws, after inspections. It can refinance your current home, or combine buying a house with adding an ADU.

Not every lender offers these loans, and some won’t finance a detached ADU, so ask early. The Freddie Mac figures come from a third-party copy of its guide; have your lender confirm them.

The appraisal sets your ceiling. An ADU can cost more to build than an appraiser thinks it adds, especially where few homes with ADUs have sold nearby. Detailed plans, a realistic bid and local ADU sales and rents help.

Factory-built ADU? Freddie Mac requires a manufactured-home ADU to be titled as real property, part of the land rather than personal property (Freddie Mac, 2024). Fannie Mae has the same rule and treats modular homes like site-built ones (Fannie Mae, 2025). See how ADUs are built.

Construction loans. These pay for a build in stages and last about as long as the project. Afterward the loan converts into a permanent mortgage or gets paid off with a new one, and terms vary widely by lender. Freddie Mac offers one exit: a no-cash-out refinance into CHOICERenovation can pay off short-term money used to build an ADU, as long as the ADU is finished by closing (Freddie Mac, 2024).

Can the ADU’s future rent help you qualify?

Often, within limits. FHA, Fannie Mae and Freddie Mac all let lenders count part of an ADU’s rent as income, under different conditions:

A made-up example: the appraiser expects the ADU to rent for $1,400 a month, so a lender counts 75%, or $1,050. With $4,000 of other monthly income, 30% of the $5,050 total is $1,515, so all $1,050 counts. With $2,000 of other income, the cap allows only about $857, which is 30% of $2,857. Under an FHA 203(k) with no rental history, 50% counts, or $700 (HUD, 2023). You still need to afford the payment when the unit sits empty.

Three things trip people up:

• Short-term rentals don’t set the number. FHA appraisers must leave out rentals shorter than 30 days when they estimate ADU rent (HUD, 2023).
• Restrictions can block FHA’s estimate. The appraiser may estimate ADU rent only if the unit can legally be rented without restrictions (same source). If your town requires the owner to live on site, or a grant limits who can rent the ADU, ask the lender whether that counts.
• Fannie Mae’s rule covers an existing ADU. For one not yet built, FHA’s 203(k) clearly counts projected rent; ask how lenders treat a new ADU under Fannie Mae or Freddie Mac renovation loans.

Are there grants or low-cost loans in New York?

ADU grants are rare, local and limited by income, and they come with rules about who can live in the unit. Treat one as a bonus, not the plan, and never pay anyone who promises to get you one.

In New York: The state’s Plus One ADU Program helps lower- and middle-income homeowners build a new ADU or bring an existing one up to code. It began in 2023, after the 2022-23 state budget set aside $85 million (NYS HCR, Jan 2026). In Round 4, the 2026 round, the grant can be up to $125,000 per ADU outside New York City and $175,000 inside it, and that cap includes the local administrator’s fee of up to 10%. Household income can be up to 120% of area median income (AMI), the middle income for your region, adjusted for family size (NYS HCR, Round 4, 2026).

In New York: Plus One money comes with strings. Under Round 4, you sign a regulatory agreement lasting at least 10 years. The ADU must be the main home of a tenant or a family member, you certify every year that it is permanent housing and not a short-term rental, and the administrator visits every two years (NYS HCR, Round 4, 2026). You must also live in the main house (NYS HCR, 2024). Any rent limits are set by each local administrator, so get the actual agreement and have a lawyer read it before you count on the money.

In New York: You apply through the local program administrator for your town, not through the state (NYS HCR, 2026). By January 2026, 14 administrators were working with more than 80 communities (NYS HCR, Jan 2026). When we checked the state’s list in October 2026, none served Monroe, Ontario, Wayne, Seneca, Yates or Steuben counties; the closest Finger Lakes-area administrator was Ithaca Neighborhood Housing Services, serving Ithaca (NYS HCR, 2026). So as of October 2026, most Rochester-area homeowners can’t use Plus One. That could change: Round 4 set aside up to $12 million for new or existing administrators, with priority for applications received by September 3, 2026 (NYS HCR, Round 4, 2026). Check the state’s Plus One page for the current list. New York City’s separate version stopped taking applications on June 12, 2026 (NYC HPD, 2026).

In New York: A grant doesn’t always cover the whole cost, so the state planned a Plus One gap loan. In January 2026 it asked CDFIs, nonprofit community lenders, to apply to run a fund of up to $3 million. The planned terms: $10,000 to $85,000 per homeowner at 0% interest, repaid over up to 30 years, secured by a lien (a legal claim) filed with the county clerk, plus a small monthly servicing fee. Only homeowners already approved for Plus One qualify, and all other money must be lined up first (NYS HCR, Jan 2026). As of October 2026, we couldn’t confirm that a lender has been chosen or that loans are being made, so check the state’s Plus One page for current status. Our New York page covers the state’s ADU rules.

What this means for you

• Start with your town, not the bank. No loan fixes a zoning “no.” Use our property checker and our guide to checking your town’s rules.
• Have three things ready before you apply: a plan your town will permit, a fixed-price bid and a local rent estimate.
• Match the tool to your situation. Lots of equity and a low-rate mortgage: ask about a HELOC or home equity loan. Little equity, or buying a house: ask about a renovation mortgage. Age 62 or older: a HUD-approved housing counselor can explain reverse mortgages (CFPB, 2022).
• Don’t count on a grant around Rochester. As of October 2026 there’s no local Plus One administrator, so plan on regular financing and check Plus One again each funding round.
• Bring in the right people. A lender decides what you qualify for. A lawyer can read a grant agreement or a HELOC’s rental clause. A tax preparer can explain how rent, loan interest and a higher assessment affect your taxes. Your assessor can tell you whether your town and school district adopted New York’s optional ADU property tax exemption (NY Real Property Tax Law §421-p). Our renting and taxes guide goes further.

What should you ask a lender?

• Do you offer HomeStyle, CHOICERenovation or FHA 203(k) loans, and will you use one for a new detached ADU?
• Will you count ADU rent on a purchase, a refinance or both? Projected rent, or only rent from an existing ADU?
• Does your HELOC contract limit renting out part of my property?
• What happens if the appraisal comes in below the project cost?

General information, not legal, tax or financial advice. Your municipality decides what can be built, and a professional should review decisions about money and contracts.