We sold our rentals, one of the happiest days of my life when we closed on the last one. Rentals are the biggest PITA imaginable, with the possible exception of owning a restaurant or bar.
They're not bad if you buy good houses that will attract good renters. The last house I bought was fairly immaculate and in a nice, yet fairly low cost neighborhood.
I'll admit, it's a bit tricky to find a rental property that's low enough in price yet still decent enough to attract good renters. You have to keep an eye out for the right one.
I got a decent deal on one I bought in October. I paid a bit under $150K for it. With 20% down I'm renting it for 2X the mortgage payment. If I put it on the market today I'd price it at $170K.
Those deals don't come along every day, though. The market is so hot around here right now for any house under $300K that any with an appropriate price will have 5 offers on the table 24 hours after it's listed.
It's a big plus to have 20% down on hand. A lot of people looking for a nice, starter home (the kind that make good rentals) will have 5% to 10% down and looking for a FHA loan.
Sellers don't particularly like FHA loans. Someone with 20% in hand and planning on financing with a conventional loan will have an edge over those other 4 offers that are on the table.