Economics and landlording are not two different things. If you think they are, you don't understand economics.
The trouble a horrible tenant will cause is worth something. It's different to every individual since some actually like and welcome trouble so they can get their hard ass hat on while other absolutely hate confrontation. Obviously the thought of a trouble tenant will push the hard ass landlord to not care as much about who comes in, but will just care more about getting someone in the unit and get money coming in. While the passive agressive landlord will screen very carefully and be fine letting his unit sit empty for a longer period of time.
If you can't field 30 calls in a 2 day period, you probably need to let a property management company take over your rental. You're obviously too busy for this sort of thing.