Free ADU Tool

ADU Feasibility Calculator

Estimate your rental income, return on investment, and project cost. Massachusetts–specific defaults built in.

Step 1 — Choose Your ADU Floor Plan
20 × 24 ft
480 SF

1 Bedroom

Compact, efficient. Ideal for a single occupant or couple. Lowest construction cost.

24 × 28 ft
672 SF

1–2 BR

The most popular configuration. Comfortable for a small family or aging parent.

26 × 34 ft
884 SF

2 Bedroom

Full-featured unit. Maximum rental income and flexibility for multigenerational use.

Property & Project Details

Step 2 — Enter your numbers

Pre-filled based on selected floor plan. Adjust for your site conditions.
Greater Boston typically 10–15%.
Pre-filled based on floor plan. Adjust for your market.
Insurance, maintenance

Get Your ADU Analysis by Email

Jack will review your numbers and send you a personalized note — including whether your town's zoning is ADU-friendly and which builders he'd recommend for your site.

✓ Received! Jack will be in touch within one business day.
© More Realty Advisors · Jack Girvan, Licensed MA Real Estate Broker · ADUExpertMA.com · 617.913.7573
Calculations are estimates for informational purposes only. Actual costs vary by site, municipality, and contractor. Consult a licensed builder and your local zoning board.

Important: Reverse Mortgage & ADU Construction

Before continuing, there are critical considerations when combining a reverse mortgage with ADU construction that most families discover too late.

  • Lender approval required: Building an ADU on a property with an existing reverse mortgage requires lender approval — which is rarely granted without significant conditions.
  • Loan may need to be paid off first: In many cases the reverse mortgage must be satisfied before a permit can proceed.
  • Compounding balance risk: At ~7.8% monthly compounding with no payments, a $400,000 reverse mortgage balance reaches approximately $870,000 by Year 10 and $1,284,000 by Year 15 — often outpacing home appreciation.
  • Sunk costs: Families who discover this restriction mid-permit have lost thousands in design and permitting fees. Title review is essential before any planning begins.

This conversation requires a financial advisor, an estate attorney, and an independent real estate advisor — not the lender originating the reverse mortgage.

Jack Girvan has navigated this scenario with many Greater Boston families. A free 15-minute conversation could prevent a costly mistake. Schedule now →