Fiance's dad does house rentals full time. Buys tax forfeitures and remodels them, rents them for a few years and sells them. He has about 5-8 at any given time. Town has about 5000 people and a shortage of homes in the 100-150 range. Abundance of 250+k new houses (and a lot of 400k+ lakeshore vacation homes) and a lot of pre WW2 wore out 60k houses with bad roofs, sketchy wiring, no garage, but not much in between. Makes it real tough to stay in business when you rent a house out that you just refinished and the first renter trashes it in 4 months and you have to remodel the thing again.
About 90% of renters are decent, that last 10% though wow. He has had your normal deadbeats, sheet rock hole punchers and drug dealers, but the worst one was the witches who screwed the windows shut and reversed the locks in the bedroom to keep their kid from getting out of the bedroom along with leaving 2 dogs and 2 cats in the house for 2 weeks after they moved out but before their move out date. They also shoved dirty diapers through the dog door in the shop he
Basically background checks only show if they are criminals. If they are deadbeats you see nothing.
Landlord/property income is good money when you have good renters, but the bad renters really hurt the bottom line.