Your house is your biggest investment, but it could also be a source of income you hadn't thought about.

Get this: In 33 of the 50 biggest metro areas in the United States, rents are higher than typical monthly mortgage payments. If you own a home in one of those cities and you're thinking about moving, it might be wiser to rent your home instead of selling it.

The typical rent-to-mortgage difference for these areas means renting could mean money left over after paying the mortgage that you could save for your dream vacation, invest for your retirement or use to pay off bills. And you'll continue to build equity in an era when home prices are on the rise. Typical U.S. home values have risen 17.7%% over the last year, the biggest increase in 25 years. Zillow economists predict increases of 11.7% by August 2022.

Rents are on the rise

Rents are rising, too. In nine of the nation's largest metros — Riverside, Calif., Tampa, Las Vegas, Jacksonville, Memphis, Phoenix, Virginia Beach, Atlanta and Miami — rents are more than 10% higher than their projected levels based on pre-pandemic trends, topping out at 15.6% higher in Tampa.

Metro areas across the South and Midwest dominated the list of cities where rents are higher than mortgages. Memphis topped the list, with rents averaging $1,504 vs. mortgages averaging just $948. That means a homeowner in Memphis could pocket around $550 per month by renting instead of selling their home. Miami came in second, with rents averaging $2,249 vs. mortgages averaging $1,727. That's a $520 difference. Atlanta came in third, with rents averaging $1,787 vs. mortgages averaging $1,363, for a $424 difference.

Other top-10 metros included Indianapolis, Orlando, Oklahoma City, Charlotte and Birmingham, Alabama.

Top 10 metros for saving money by renting out properties

Your single-family home could be a renter's upgrade

Renting out your single-family home may not only be a win for you, it could be a win for renters who want out of apartments, which make up most of the nation's rental properties.

'Single-family homes comprise about one-third of the nation's total rental stock,' said Zillow economist Alexandra Lee. 'Owners who do rent out their properties can provide both much-needed rental inventory in tight markets as well as sought-after space and amenities for families looking to move up from an apartment.'

If you're not moving out of your house and can afford a down payment, you could consider buying a house and renting it out. Seven out of 10 rental properties in the U.S. are owned by individuals who own just one or two properties, according to a Pew Research Center study.

Crunch the numbers with our calculator

Being a landlord comes with some responsibilities and expenses. You'll need to screen prospective tenants, and you will still be responsible for maintenance on the house and appliances. You'll also have to pay for insurance, pest control and HOA fees (if applicable). If you hire a property manager instead of DIY-ing it, expect to pay 8% to 12% in management fees.

So before you take the plunge and become a landlord or add a second property to your real estate investment portfolio, you should determine whether the property you're eyeing will have 'cash flow.' That's the industry term for whether an investment property will produce money after all the expenses are paid.

Use our rental property ROI calculator to crunch the numbers to see a ballpark figure of what you could earn renting your house over 5, 10, 20 or 30 years. The number may surprise you.