But how does your plan to host short-term renters play out when you’re applying for a mortgage? Rent money will increase your yearly earnings, but do lenders count future revenue as income? Can plans to maintain a short-term rental help you get a mortgage?

For the most part, no. Stephen Rybak, senior managing director at GuardHill Financial Corp., says a lender will never consider potential income from renting out part of a single-family home. And it doesn’t matter if we’re talking about a space that’s detached from the house (e.g., a garage apartment, studio, or casita)—it’s all technically part of a one-family home.

“If it’s not zoned for a two-family, you’re never going to get credit for that from a lender,” he says.

Two-family properties

You will, however, be able to include part of your potential rental income if you are buying a building zoned for two or more families. Whether it’s a townhouse, brownstone, or free-standing home with multiple units, the building needs to be a legal two-family dwelling.

How a lender decides what your rental is worth

In a two-family or multifamily home, the market-rate rent for each unit is determined during the appraisal process.

“The appraiser will give you the market value,” says Rybak, “and the bank will consider 75% of that amount to help you qualify for the loan.”

So if you’re buying a two-family home and the appraiser puts the fair market rent for your unit at $1,000 a month, you’ll get $750 a month, or $9,000 a year, added to your income. That will allow you to qualify for a bigger loan than you otherwise would have been able to get—regardless of what you actually end up making on the rental.

Could short-term rentals hurt your ability to refinance?

Just because the bank won’t consider income from a short-term rental in a one-family home doesn’t mean you shouldn’t do it. Renting out your place is still a great way to help pay your mortgage.

However, keep in mind that, in rare situations, having an active short-term rental could hurt your ability to refinance. If your lender decides that you make enough money from your home to qualify as a commercial or investment property, it could deny your refinance application or charge you a higher interest rate. That means the $30,000 you make a year renting out the cottage behind your home could disqualify you from refinancing the whole property. In this situation, a bank could consider you to be operating a business out of your home.

That kind of issue is rare, though. So if short-term rentals are legal in your city, and you don’t mind taking on the responsibilities of being a property manager, a supplemental income—potentially thousands of dollars a year—is nothing to sneeze at.