I have some cases that tenants actually were drag dealer. They asked wife/girl friend to lease my property, and moved in. I can not check their background. After they move in I have no way to prove they live there long term. I have to find other excuses like lease violation (fail to maintain the property), city citation for trash/tall grass to evict them.
In one case, I have no choice but let FBI ruin the peoperty.
I know some landlord would talk to the tenant about illegal activities complaint. And tell them the police is watching. They'd better move ASAP. Sometime it works.
Good luck!