Here is an interesting article that talks about rents vs mortgages.
If you are thinking about becoming a landlord, don't expect your rent to cover your mortgages at this time.
Mortgage meltdown: Vulture investors - The rent increases should provide a price-safety net, especially for condos, since investors will buy as the spreads between rents and mortgage payments diminish. Today the nationwide median mortgage payment of $1,566 is still 80 percent higher than the median monthly rent of $943, but that's down from a couple of years ago, when the difference was close to 100 percent.
There will always be people that owning a house is just out of reach and have to rent. IMO it all boils down to what you want the rental income to do for you.
If you are in it as your primary income, you need lots of apartments with paying tenants. You will always need to keep the rentals occupied. Lots of money will grow legs to fix things. And you had better be handy with tools.
If its to supplement your income, it can be less stressful with more money sticking to your back pocket.