I always look closely at this during the purhase process and particular so if the lease just started because LLs will put crappy tenants in just to keep the place full but know they won’t have to deal with them. If they are m2m and I have the least bit of trouble, I give they 30 days notice. That was my mistake in the past is I knew I had crappy tenants (i.e. ragin’ out my prop.), but the rent came in so I put off dealing with it.
When a lease expires, I make them fill out a new application and put them on a new lease. The application is a formality as usually after a couple of months, you know what kind of people you are dealing with, but the application is nice since it give a window into their employment situation which is otherwsie difficult to assess. If people get up and got to work every day, the rent is likely to the paid. Sketchy employment means not only the rent might not get paid, but more chance of late night drinking, parties, and all the bad things that come along with that (none of which are good for you as the owner of the property).