WASHINGTON — If you are considering renting out a room for extra cash, the best places are outside the Beltway.

The best market for renting to millennials is Baltimore City. RealtyTrac analyzed population trends and housing data in hundreds of markets and found that Philadelphia came in at number two on the list. Prince William County, Newport News, Richmond, and Virginia Beach all made the top 50.

Baby boomers, on the other hand, are heading south. Pasco County, Florida was ranked number one, with 15 other Florida counties rounding out the top 25.

When it comes to buying single family properties to rent out, the best areas around the D.C. area are Spotsylvania County (number five) and Frederick County, Maryland (number 13).

The analysis found rental returns by calculating the annual gross rental yields using the average fair market rent of three-bedroom homes in the county, annualized, and divided by the median sales price of residential properties in the county.

Follow @WTOP on Twitter and on the WTOP Facebook page.