Heck, it doesn't really even have to appreciate... If the rental is done right you are having someone paying off the mortgage. It's just deferred income. I'm stuck with a rental where I used to live. I am under by $70 / month with the rent I'm giving but that parlays into $550 being paid a month on my principal by the renter. $550 for $70 isn't bad return. I'm not selling it because it's 3 years from paid off and it's in a slow mover location (would be on the market for 6-8 months). So I'm just waiting until I'm making $550 a month instead of the bank. Or I could sell it and get the sale price out of it once it's paid off. Which would be 18 years to make $120k on 15k.

I probbably should have sold it long ago but $70/month is like internet.