How to Finance an ADU in Massachusetts

Building an ADU in Massachusetts became a lot more achievable in the last two years. Zoning is no longer the main obstacle for most homeowners. Financing usually is.

If you're trying to figure out how to pay for an accessory dwelling unit on your property, here's an honest look at the options available right now, including a new state program that changes the math for a lot of homeowners.

Why ADU financing is different from a typical home renovation loan

Most home equity products assume you're adding value to your existing living space like a a new kitchen, a finished basement or an addition. An ADU is a bit different because you’re creating a second, independent home on your property, and most lenders haven't fully caught up to that.

MassHousing's ADU loan program

In March 2026, MassHousing launched a statewide loan program built specifically for ADUs. A few things make it a great option:

How much you can borrow: Up to $250,000 for a detached ADU and $150,000 for an attached ADU , structured as a second mortgage.

How the rate works: The loan is split into two parts. One portion carries a fixed rate of 5.25% over 20 years. A second portion carries 0% interest with deferred repayment. Combined, the blended rate ends up lower than most standard home equity products, and the overall amount you can borrow goes up.

Who qualifies: Income limits are set at 135% of area median income. In eastern Massachusetts, that works out to a household income limit of roughly $205,000, which covers the large majority of homeowners in Greater Boston. Limits are lower in other parts of the state, closer to $165,000 in Worcester County and $130,000 in Hampden County.

The catch: This loan doesn't fund a project from the ground up. Before MassHousing will lock in financing, your project has to be "dig ready," meaning permitted, designed, and fully documented. The money comes after the planning, not before it.

That last point is the most important one. It means the feasibility study, civil engineering, and permitting work all have to happen before you can access this financing. Homeowners who try to find a lender first and figure out the project second usually end up stuck.

Other ways homeowners are financing ADUs

The MassHousing program is the newest option, but it's not the only one. Depending on your situation, you might also consider:

Home Equity Line of Credit or HELOC. Still the most common way homeowners fund ADU construction, especially if you've built up significant equity and don't qualify for, or want to avoid, the more restrictive eligibility rules tied to state programs or construction loans. If you have enough equity in your home, it

Cash-out refinancing. Worth running the numbers on if your current mortgage rate isn't dramatically lower than what's available now. If you had a high rate last year and are looking to refinance anyway, this could be a great option

Construction loans. More commonly used by general contractors and builders than individual homeowners, but an option worth discussing with your lender if you're building from scratch and need funds released in stages. Local banks like Reading Cooperative have loans specifically designed for ADU Construction, and they help streamline the process because they understand how and why ADUs are built.

Family financing arrangements. A growing number of ADU projects in Massachusetts are funded by the family members who will actually live in the ADU. Adult children, for instance, taking out a loan to build a unit for aging parents, while the parents eventually transfer the property. These arrangements work, but they deserve a real conversation about ownership, inheritance, and what happens long-term, not just a financing decision made in isolation. In this situation, we highly recommend talking with a wealth-planning attorney that can create a legal agreement for all parties.

The real first step isn't financing. It's feasibility.

Every financing option above, including the new MassHousing program, depends on knowing what you're actually building, what it will cost, and whether your lot and town will allow it.

That's what a feasibility study answers. It's the step that turns "I'm interested in an ADU" into a plan a lender, a bank, or a state program can actually finance.

If you're a Greater Boston homeowner trying to figure out how to pay for an ADU, the first conversation worth having isn't with a lender. It's about whether your project is actually buildable, and what it will cost to get there.

Frequently Asked Questions

Can I use the MassHousing ADU loan for any type of ADU?
The program is designed for ADUs that meet Massachusetts' by-right zoning requirements under the Affordable Homes Act, generally units under 900 square feet, whether attached, detached, or a conversion of existing space like a garage or basement.

Do I need good credit to qualify?
MassHousing's program follows standard mortgage underwriting, so credit history and debt-to-income ratio matter, similar to qualifying for a second mortgage through a conventional lender. Specific credit score thresholds depend on the participating lender.

How long does it take to get "dig ready"?
It varies by town and project complexity, but feasibility, design, and permitting typically take a few months before a project is ready to apply for this kind of financing. Lot conditions, your town's specific zoning review process, and whether utility connections are straightforward all affect the timeline.

Can I combine this loan with other financing, like a HELOC?
Possibly, depending on your existing mortgage and total debt load. This is a conversation to have directly with your lender, since combining loan products affects your overall borrowing capacity.

What happens if my project costs more than the loan covers?
This is common, especially on older homes where unexpected upgrades come up during construction. Most homeowners pair this loan with personal savings or a smaller secondary loan to cover the gap. It's also why having an accurate cost estimate before applying matters more than people expect.

Is the MassHousing program only for homeowners planning to rent out the ADU?
No. It's used just as often for family situations, housing a parent, an adult child, or a caregiver, as it is for rental income. The loan program doesn't require a specific use case, but your individual financial goals should shape which financing option makes the most sense.

If you’re ready to start your ADU journey, we’d love to chat. Click below to schedule a free 15-minute call.