@Dominika M When I got started there was only one other guy I knew of who did RTOs on a regular basis here in the Kitchener-Waterloo area, and he was a realtor. He did it as a way to get a quick and easy commission on leads other agents wouldn't touch (sellers with no equity, buyers with no down payment).
Nowadays it seems everyone has jumped on the bandwagon, from individual landlords, to corporations, to several of the big-name realtors.
As @Roy N. said it's mostly in the starter home price range.
These can be a good deal for everyone involved if you don't get greedy. I'm looking for sellers who bought recently with a nice low interest 5 year mortgage. They typically have no equity and are just looking to breakeven and get out from under their payments. I'll buy their home for what they owe on a contract deferred to the renewal date of their mortgage.
Then I'll look for a buyer who doesn't quite have 5% to put down and maybe has a few credit issues. With 3-5 years on the mortgage I've got plenty of time to work with them to get sorted for financing. If that doesn't work and they've been a great customer (responsible with payments, take good care of the property) I'll assume the mortgage myself and keep them on until they can pay me out completely.
I shoot for about a 10% spread on both price and payments for my profit, so over the course of the deal, the buyer ends up with the lions' share of any appreciation or capital improvements that they make to the home.
Hope that helps!