We build ADUs across Eastern Massachusetts and Southern New Hampshire, and we walk through financing with homeowners before design work even starts. The goal is always the same: match the right loan product to the project so that draw schedules, permitting milestones, and construction phases all move together instead of fighting each other.

Most homeowners we work with use one of four funding paths. Each has different equity requirements, approval timelines, and draw structures, so comparing terms before committing to a design matters.

Home equity line of credit (HELOC) draws against equity already built up in the primary home. Funds pull as needed during construction, and you only pay interest on what you have drawn. For homeowners with strong equity positions, this is often the fastest route to breaking ground.

Cash-out refinance replaces the existing mortgage with a new, larger one and gives the difference in cash. In 2026, this option is less attractive for homeowners who locked in sub-4% rates during 2020-2022. It only makes sense when current rates are close to what you already carry.

MassHousing ADU loan program is a state-supported option worth knowing about. MassHousing announced a dedicated ADU construction loan in early 2026. The program offers a fixed-rate second mortgage that finances up to $250,000 for detached units and up to $150,000 for attached units. It is structured as a 20-year loan paired with additional zero-interest deferred funding to lower the effective rate for borrowers. Eligibility and terms are set by MassHousing, so confirm current details directly with the agency before applying.

Yes. A HELOC covers the same phases as a dedicated construction loan: design fees, permit filings, and construction draws. Many homeowners across the North Shore and Merrimack Valley already carry meaningful equity, which makes this option accessible without a separate loan application.

There are three things lenders look at before approving a line of credit against a primary residence:

Credit profile is payment history and credit score. A strong equity position alone does not guarantee approval. Credit carries equal weight.

Debt-to-income ratio (DTI) measures existing monthly obligations against income. Even high-income households get turned down if DTI is stretched too thin by other debt.

Both paths fund the same underlying work. The real difference comes down to structure and timing.

A HELOC moves faster if equity is already in place. Draws happen without milestone inspections, which gives more flexibility during construction. The tradeoff is that most HELOCs carry variable rates, so the long-term payment is less predictable than a fixed construction-to-permanent loan.

The calculation is straightforward. Take the realistic monthly rent for a comparable unit in your town (not the optimistic number, the one a property manager would quote), subtract the monthly loan payment, insurance, and maintenance costs, and see what is left. If the net number is positive from month one, the ADU is cash-flow positive immediately. If it takes 12-18 months of rent to get ahead of closing costs and finishing expenses, that is still a strong return compared to most home improvements.

Financing structure changes how quickly you reach that break-even point. Interest-only draw periods on a HELOC keep early costs low while the unit is being built. A construction-to-permanent loan locks in a steady fixed payment sooner, which makes long-term budgeting simpler.

For homeowners still early in the numbers, our financing resources page walks through budgeting considerations before you commit to a design.

Here is what to have ready:

Equity and DTI numbers. Know what you owe on the house, what it appraises for, and what your monthly debt obligations look like. A lender will calculate this anyway. Knowing it yourself beforehand saves a round trip.

Projected rental income. If the ADU will generate rent, documenting comparable rental rates in your town strengthens the application. Lenders increasingly factor projected rental income into qualification, especially under newer guidelines that allow ADU rental income to count toward mortgage approval.

Permit feasibility. Massachusetts now allows one ADU by right in single-family zoning districts statewide. New Hampshire permitting still runs town by town. Either way, confirming that the property qualifies for an ADU before applying for financing avoids wasted time and application fees.

What is the fastest way to finance an ADU in New England? A HELOC is typically the fastest path if you have sufficient equity in your home. Draws can begin as soon as the line is approved, without the milestone inspections required by a dedicated construction loan. Many of our clients in the North Shore and Southern NH use a HELOC to keep the project moving without delays between phases.

How much equity do I need to finance an ADU with a HELOC? Most lenders require at least 15-20% equity in the home, though some ADU-specific HELOC products go higher on combined loan-to-value ratios. Your credit score, debt-to-income ratio, and income verification carry equal weight in the approval decision.

Will rental income from my ADU help me qualify for the loan? Increasingly, yes. Newer lending guidelines allow projected ADU rental income to factor into mortgage qualification. Documenting comparable rental rates in your area and presenting a realistic project budget strengthens the application. We help homeowners put together that documentation as part of the project planning process.