The quick read: Yes, an investor can finance a Boston triple-decker with a DSCR loan, as long as no owner plans to live in it. The lender divides the three units' monthly rent by the full monthly payment, which NerdWallet's DSCR guide (updated July 17, 2026) says includes principal, interest, taxes, insurance and homeowners association fees, and NerdWallet says lenders typically want a ratio of around 1.25 or higher. Two Boston facts decide whether the file holds up. First, taxes: the city's fiscal 2026 residential rate is $12.40 per $1,000, and the residential exemption that can cut a seller's bill by up to $4,353.74 is only for owners who live in the property. Second, short-term rentals: Boston lists investor-owned units as ineligible to register, so nightly-rate income on an investor-owned triple-decker does not belong in the ratio.
Can you get a DSCR loan on a Boston triple-decker?
Yes, an investor can get a DSCR loan on a Boston triple-decker when the building is a business-purpose rental that no owner occupies, because the lender sizes the loan on the three units' rent against the full payment. If the buyer plans to live in one unit, the analysis changes.
The ratio is a single division: monthly rent over the monthly payment. A DSCR calculator runs it in seconds. NerdWallet describes typical lender terms this way, and each lender writes its own sheet, so treat these as a starting point, not a market rule:
Typical minimum DSCR (NerdWallet, updated Jul 17, 2026): around 1.25 or higher Credit score (NerdWallet, updated Jul 17, 2026): at least 620 Down payment (NerdWallet, updated Jul 17, 2026): at least 20% Reserves (NerdWallet, updated Jul 17, 2026): three to six months of mortgage payments Prepayment (NerdWallet, updated Jul 17, 2026): most DSCR loans come with prepayment penalties
Occupancy is the line that matters on a three-family building, because many triple-decker buyers plan to live on one floor. The CFPB's official interpretation of Regulation Z (comment 3(a)-4) deems credit to acquire, improve or maintain rental property that is not owner-occupied to be for business purposes regardless of the number of housing units, and an owner who expects to occupy the property for more than 14 days in the coming year cannot treat it as non-owner-occupied. Comment 3(a)-5 covers owner-occupied rental property: credit to acquire it is deemed business purpose if it contains more than 2 housing units, and credit to improve or maintain it only if it contains more than 4. So buying an owner-occupied triple-decker is deemed business-purpose credit under that commentary, but a later renovation loan on the same building is not automatically deemed business purpose, and NerdWallet says a DSCR loan can't be used to buy a primary residence. If you will move in, ask for a residential mortgage quote as well.
How do Boston property taxes and the residential exemption change the DSCR?
Boston property taxes sit inside the payment a DSCR lender divides into rent, and the city's fiscal 2026 residential rate of $12.40 per $1,000 applies to the full assessed value for an investor, because the residential exemption, worth up to $4,353.74 last fiscal year, is reserved for owners occupying the property as a principal residence.
Boston taxes residential and commercial property at different rates. The Assessing Department's tax page (last updated 1/1/26) says the city operates under a property tax classification system and lists the 2026 rates:
Residential rate, fiscal 2026 (City of Boston Assessing, updated 1/1/26): $12.40 per $1,000 of value Commercial, industrial and personal property rate, fiscal 2026 (City of Boston Assessing, updated 1/1/26): $26.96 per $1,000 of value Residential exemption, maximum saving last fiscal year (City of Boston Assessing, updated 7/1/26): up to $4,353.74
The exemption is the Boston trap. The Assessing Department's residential exemption page says homeowners must own and occupy the property as a principal residence to qualify, and that fiscal 2027 runs from July 1, 2026 through June 30, 2027. A triple-decker sold by an owner who lived on one floor can carry that exemption on the seller's bill. An investor buyer will not qualify, so a model copied from the seller's bill can understate the tax line by up to $4,353.74 a year, about $362.81 a month (our arithmetic).
Mixed-use buildings add a second rate. If part of a building is classified commercial, such as a corner store under two apartments, that part is taxed at the commercial rate. Per $100,000 of assessed value, the fiscal 2026 rates work out to $1,240 a year residential against $2,696 a year commercial, a difference of $1,456 a year, about $121.33 a month (our arithmetic). Ask the Assessing Department how the parcel is classified before you size the loan.
What does the DSCR math look like on an illustrative Boston triple-decker?
On an illustrative $1,200,000 Boston triple-decker renting for $9,000 a month, a $900,000 loan at 7.00% produces a DSCR of about 1.19 once taxes are built at the fiscal 2026 residential rate without the exemption, below the roughly 1.25 NerdWallet says lenders typically want. A smaller loan closes the gap.
Every input below is an assumption chosen for illustration, not a quote, a market rate or a Boston rent survey. The tax line assumes the assessed value equals the price; the actual assessment will differ.
| Illustrative triple-decker line (our arithmetic) | Monthly amount | Basis |
|---|---|---|
| Illustrative triple-decker line (our arithmetic) Gross rent, three units at $3,000 | Monthly amount $9,000.00 | Basis Assumption |
| Illustrative triple-decker line (our arithmetic) Principal and interest, $900,000 at 7.00%, 30-year amortization | Monthly amount $5,987.72 | Basis Standard amortization, 75% of value |
| Illustrative triple-decker line (our arithmetic) Property tax, no residential exemption | Monthly amount $1,240.00 | Basis $1,200,000 x $12.40 per $1,000, divided by 12 |
| Illustrative triple-decker line (our arithmetic) Insurance | Monthly amount $350.00 | Basis Assumption |
| Illustrative triple-decker line (our arithmetic) Total payment | Monthly amount $7,577.72 | Basis Sum of the three payment lines |
| Illustrative triple-decker line (our arithmetic) DSCR | Monthly amount 1.19 | Basis $9,000.00 divided by $7,577.72 |
Now copy the seller's bill instead. If it carried the full $4,353.74 exemption, the tax line would fall to $877.19 a month, the payment to $7,214.91 and the ratio to about 1.247. The spreadsheet nearly clears 1.25; the building does not, because the investor never gets that exemption.
To reach 1.25 on the same rent, the payment can be no more than $7,200.00. Subtract $1,240.00 of tax and $350.00 of insurance and $5,610.00 is left for principal and interest, which at 7.00% over 30 years supports a loan of about $843,000, roughly 70% of the $1,200,000 value (all our arithmetic). The levers are the loan size, the documented rent on each floor, and the insurance quote.
Can short-term rental income count on an investor-owned Boston triple-decker?
No, a short-term rental on an investor-owned Boston triple-decker cannot be registered, because the city's rules list investor-owned units as ineligible and limit short-term rentals to owner-occupied one-to-three-family buildings. A DSCR model built on nightly rates for a building no owner lives in is modeling income the city will not register.
The Inspectional Services short-term rental page (last updated 12/16/19) sets out three registration categories, all tied to the owner's primary residence:
Limited Share (City of Boston ISD, updated 12/16/19): part of the owner's primary residence, owner present during each rental, $25 a year Home Share (City of Boston ISD, updated 12/16/19): the owner's primary residence, owner not present, $200 a year Owner-Adjacent (City of Boston ISD, updated 12/16/19): one full unit in the same two- or three-unit property as the owner's primary residence, $200 a year Primary residence test (City of Boston ISD, updated 12/16/19): the owner lives in the property at least nine months out of a 12-month period
The same page says Limited Share and Home Share units must be in owner-occupied single-family, two-family or three-family buildings, that in a two- or three-family building the owner-occupant must own all units, and that investor-owned units are ineligible. The Owner-Adjacent category is the one door a triple-decker opens, and it requires the owner to live in the building, which takes the deal out of the non-owner-occupied DSCR file. For an investor, underwrite the building on 12-month leases.
What other Boston rules should be in a triple-decker DSCR file?
Beyond taxes, a Boston triple-decker DSCR file should show the property's rental registration with the city and its lead-paint position under Massachusetts law, because both create costs or delays that a lender, an appraiser or a tenant can surface after the rent roll looks clean. Neither appears in the ratio itself.
Rental registration comes first. The city's rental registration page (last updated October 30, 2025) says owners of rental property must register it, including vacant properties and properties under renovation:
First-time registration (City of Boston ISD, updated Oct 30, 2025): $25 for each unit Renewal registration (City of Boston ISD, updated Oct 30, 2025): $15 for each unit Maximum (City of Boston ISD, updated Oct 30, 2025): $2,500 for each building, or $5,000 for each complex Inspection (City of Boston ISD, updated Oct 30, 2025): at least once every five years after registration
Lead paint is the larger exposure on older wood-frame housing. Massachusetts General Laws chapter 111, section 197 says that whenever a child under six years of age resides in premises where paint, plaster or other accessible structural material contains dangerous levels of lead, the owner shall abate or contain it. On a triple-decker, that obligation can arrive with a new tenant, so ask the seller for any lead inspection or compliance letters and price the abatement risk into reserves before you sign.
Which lender types finance a Boston triple-decker on DSCR?
DSCR and non-QM investor lenders are the main route for a non-owner-occupied Boston triple-decker, with portfolio banks and credit unions as alternatives that may weigh the borrower's finances alongside the building. Because a triple-decker has three units, it stays inside the federal bank lending guidelines' one-to-four-family category rather than the five-plus multifamily one.
DSCR and non-QM investor lenders. These lenders qualify the deal on the property's coverage ratio. Their published minimums differ, so compare the ratio, leverage, reserve requirement and prepayment schedule in writing, side by side.
Portfolio banks and credit unions. A bank that keeps the loan sets its own coverage and pricing. The federal benchmark is the interagency real estate lending guidelines (12 CFR Part 34, Subpart D, Appendix A, 2025 edition), which set a supervisory loan-to-value limit of 85% for improved property and include 1- to 4-family residential property that is not owner-occupied in that category. The guidelines set no such limit for permanent mortgages on owner-occupied 1- to 4-family property. The limit is supervisory, not a hard cap: the guidelines let a bank make a limited volume of loans above it, and a bank can also use a lower internal limit, so ask for the actual number.
Five units and up. The same guidelines list residential property with five or more dwelling units as a separate type of improved property, so a plan to add units until the building reaches five moves it into a different lending category.
The stock is old, not new. The Census Bureau's 2025 annual building permits file for the City of Boston shows 228 one-unit buildings, no two-unit buildings and 4 three-and-four-unit buildings carrying 12 units permitted in 2025, against 71 buildings of five or more units carrying 1,867 units. With so few new three- and four-unit buildings being permitted, the triple-deckers an investor can buy are overwhelmingly existing, older stock, which is why lead, insurance and deferred maintenance belong in the underwriting conversation.
How do you get lenders competing for a Boston triple-decker DSCR loan?
You get lenders competing on a Boston triple-decker by sending each one the same complete package, with the leases, a tax figure built without the residential exemption, the registration record and the target loan size, so the quotes come back comparable. YieldStack is an AI-native commercial mortgage brokerage that arranges financing for commercial real estate investors.
YieldStack's software matches the deal against a catalog of 20,000+ loan programs, which is a count of programs, not of lenders. Human brokers then structure the request, negotiate for the borrower and carry the deal toward closing. Every credit decision is made by the lender; YieldStack arranges the introductions and negotiates on the borrower's side, and no loan, rate, or closing is guaranteed.
What to send:
- Property address, parcel ID and the current tax bill, with any residential exemption visible
- The current lease and rent for each of the three units, plus vacancy history
- The city rental registration record and any lead inspection or compliance letters
- An insurance quote or the current declarations page
- Purchase contract or payoff statement, and any planned renovation scope
- Target loan amount, expected hold, and how much prepayment penalty you can accept
The Boston market hub collects our Boston material and the Massachusetts market hub covers the rest of the state; neither is a promise of any particular lender or term. When the package is ready, send the deal for review. It costs Zero upfront to submit a deal and review offers; YieldStack's broker fee is 0.50–1.00% of the loan amount and is paid only at closing.
The bottom line
A DSCR loan on a Boston triple-decker works when no owner lives there and the documented rent covers the full payment. Build the tax line at the fiscal 2026 residential rate of $12.40 per $1,000 without the seller's residential exemption, check whether any part is classified commercial, leave out short-term rental income the city will not register, and size the loan to the ratio that is left.