Boston Neighborhood Mortgages: Triple-Decker Condos, STRs and City of Boston ONE+Boston Grants
Updated October 2026
Buying one floor of a Dorchester triple-decker is financially different from buying the entire building. The first is a condominium with shared obligations; the second may qualify as an owner-occupied multifamily purchase. Across South Boston, Jamaica Plain and East Boston, identifying that ownership structure early prevents avoidable financing surprises.
Read the small-association documents
A three-unit association may have modest dues because owners handle repairs informally. That does not make the roof, siding or master insurance inexpensive. Request the budget, reserve balance, meeting records, insurance policy and any planned assessments before treating low dues as a permanent saving.
- Confirm which expenses the association pays and which belong to individual owners.
- Check whether major work has been completed, funded or merely discussed.
- Review rental restrictions and the number of investor-owned units.
- Establish responsibility for porches, decks, exclusive-use yards and exterior stairs.
Short-term rentals introduce separate questions. Boston registration requirements, condominium restrictions, insurance terms and mortgage occupancy rules all matter. Do not build affordability around projected nightly rental revenue without confirming that the activity and income treatment are acceptable.
Separate ONE Mortgage from ONE+Boston assistance
Massachusetts Housing Partnership (ONE Mortgage) offers eligible buyers a low-down-payment structure, generally starting at 3% down, with no private mortgage insurance and income-based interest assistance. Property type can change down-payment requirements, particularly for three-family purchases.
ONE+Boston builds on that framework for eligible Boston buyers through city-supported benefits. Grant amounts, funding availability, residency requirements and participating-lender rules should be established before an offer relies on them. Assistance is not an automatic credit attached to every Boston purchase.
MassHousing provides another route, including down payment assistance that may reach $25,000 to $30,000 under applicable program terms. Compare total payment, assistance repayment obligations and required cash rather than choosing by the largest advertised amount.
Coordinate condition, contracts and cash
Older neighborhood housing deserves a clear lead-paint review. Massachusetts Lead Law obligations can become especially important when a child under six lives in the property; ownership conversion does not remove those responsibilities.
Have your attorney coordinate the Offer to Purchase, Purchase & Sale agreement and condominium review with your financing contingency. Budget prepaid expenses and reserves separately from the down payment.
Compare scenarios in the monthly payment calculator, then use the closing cost estimator to identify the remaining cash gap after confirmed assistance. Saltbox & Seam’s Boston mortgage hub adds the county-limit and residential-exemption context.
Compare Current Mortgage Rates
Compare current APRs, points, fees, and estimated monthly payments from participating lenders below.
Loan Program Comparison: 2026 Benchmarks
Boston Neighborhood Mortgages: Triple Decker Condos, STRs and City of Boston ONE+Boston Grants — Choose a mortgage by comparing eligibility, upfront cash and total monthly costs, not the advertised rate alone. Conventional, FHA, VA and USDA serve different borrowers. Confirm county limits, taxes, insurance and lender requirements before comparing personalized Loan Estimates for your household.
Historical 2025 one-unit comparison: conforming $806,500; FHA floor $524,225. County and unit-count limits can differ.
| Loan program | Down payment / equity | 2026 one-unit baseline | Costs and page-specific comparison |
|---|---|---|---|
| Conventional | 3%–5% subject to eligibility | $832,750 | PMI generally below 20% down |
| FHA | 3.5% at 580+; 10% at 500–579 | $541,287 floor | 1.75% upfront MIP; 0.55% annual for >95% LTV, base loan ≤$726,200, term >15 years |
| VA | 0% for eligible borrowers | No VA limit with full entitlement | No monthly PMI; funding fee unless exempt |
| USDA | 0% for eligible borrowers | Income, address and repayment eligibility | Guarantee and annual fees; confirm current schedule |
| Jumbo | Lender-specific cash and reserves | Above applicable conforming limit | Lender-specific pricing and insurance |
| Home Equity / Refinance | Equity and underwriting dependent | Property and lender dependent | Compare closing costs, term and break-even |
Sources: FHFA limits; HUD FHA limits.
Editorial Methodology & Primary Sources
Verification date: Not recorded; check the primary source and lender timestamp before relying on an estimate.
Rate comparisons use participating lender feeds, not a whole-market survey or guaranteed offers. Freddie Mac PMMS is a market benchmark, not a personalized quote. Calculator models rely on published regulatory formulas and disclosed assumptions rather than fabricated first-person loan testing.
Monthly principal and interest use the amortization formula P × r / (1 − (1 + r)−n), where r is the monthly note rate and n is the number of payments; at zero interest use P / n. PITI adds monthly property taxes and homeowners insurance; PMI is separate. APR includes applicable finance charges under Regulation Z and is not the note rate used for payments. Compare lender Loan Estimates for actual APR and fees.
- Consumer Financial Protection Bureau (CFPB) — Loan Estimates, APR and borrower disclosures; Regulation Z.
- U.S. Department of Housing and Urban Development (HUD / FHA) — FHA program guidance.
- U.S. Department of Veterans Affairs (VA) — VA loan eligibility and benefits.
- Freddie Mac Primary Mortgage Market Survey (PMMS) — published rate benchmarks.
- U.S. Census state tax collections — state property tax benchmarks; confirm parcel-specific assessments and exemptions with the state revenue department and local assessor.
The payment snapshot uses illustrative annual taxes of 1% of home price, $1,200 insurance and 0.5% PMI below 20% down, not verified local quotes. Other calculators disclose their inputs and assumptions. Published guidance and lender feeds may change independently; confirm current program rules, taxes and offers before a decision.