What Is Mortgage Offset?
Mortgage offset is how much of your housing payment gets covered by rent from other units. If your piti is $2,000 and the other units bring in $1,800, your offset is $1,800—you're effectively paying $200 for housing. A full offset means you live for free. It's the main reason house-hacking works: your tenants subsidize your mortgage while you build equity.
Mortgage offset is the portion of your housing payment (PITI) that is covered by rental income from other units in the property—the core benefit of house hacking.
At a Glance
- What it is: Rental income that covers your share of the mortgage payment
- Why it matters: Reduces or eliminates your housing cost
- Full offset: Rent from other units ≥ your total PITI
- Partial offset: Some of your payment is covered; you pay the rest
- Best case: Offset exceeds PITI = positive cash-flow while living there
Mortgage Offset = Rental Income from Other Units − Your Share of PITI
How It Works
The math. You buy a triplex. You live in unit 1. Units 2 and 3 rent for $1,100 and $1,150. Total rent from "other" units: $2,250. Your piti is $2,100. Mortgage offset = $2,250. You're covered—and have $150 left over for operating-expenses or reserves.
Allocating expenses. Some investors allocate operating-expenses (taxes, insurance, maintenance, vacancy-rate) proportionally. If your unit is 1 of 3, you might assign one-third of expenses to "your" share. That gives a more realistic effective-rent and true offset.
The goal. Full or over-offset means your housing cost approaches zero. You're building equity with someone else's rent. When you move out and rent your unit too, the property becomes a full rental-property with cash-flow.
Financing impact. Low-money-down loans (FHA, conventional owner-occupied) keep PITI lower, making full offset easier to achieve.
Real-World Example
Jake in Cincinnati. Jake bought a fourplex for $320,000 with 5% down. His piti was $2,180. He lived in one unit. The other three rented for $950, $1,000, and $1,050—$3,000 total. After 8% vacancy-rate reserve and his share of maintenance, his effective-rent from the three units was about $2,350. His mortgage offset was $2,350. He paid roughly $0 out of pocket for housing (the surplus covered his unit's share of expenses). He lived for free for 22 months before refinanceing and moving.
Pros & Cons
- Reduces or eliminates housing cost
- Build equity with tenant rent
- Low-money-down financing makes offset easier
- Accelerates path to next property
- Requires living in a multi-unit
- Vacancy reduces offset
- Operating-expenses can eat into offset
Watch Out
- Overestimating rent: Use rental-comps, not wishful numbers
- Ignoring expenses: Factor vacancy-rate, maintenance, capex
- Rate reset: Refinance when you move out can raise payment
Ask an Investor
The Takeaway
Mortgage offset is the engine of house hacking: rental income from other units pays your housing bill. Aim for full or over-offset when you run the numbers. It's how you live for free while building wealth.