I have a house and 4 flats that I've rented out for the past 17 years. I have never had any problems with any tenants. I use a very good local agent to find me tenants. They do all sorts of financial checks and require multiple references from the tenants employers and previous land lords. This tends to weed out the riff raff. Also I have a few very long term tenants who are very reliable and I have not increased the rent for years as I don't want to lose them.