Amen, Danny, they move to the next available property.
Financed some apartments in Alabama many years ago. Property behind it had a rough reputation - drugs, prostitution, a little gang recruiting.
The owner finally cracked down and the BGs moved onto our property. The owner statred having increased expenses and high vacancies.
I called him about it and he said things were bad. People were shooting guns on-site and everything. I told him to get with the local police, etc.
Three days later I get an envelope in the mail with what feels like empty .22 casings taped to cardboard. Sure 'nuf, inside were 12 casings and a note..."Just in case you didn't believe me!"
I did believe him, but figured he needed a visit, so I flew down, met with him and the local law enforcement. Moved a deputy into one of the apartments and a local PD K9 officer would come by on a regular basis. The dog destroyed a lady'd
Took about a month for the BGs to move out, trashing the apartments as they left, and move about three miles up the road to what they thought was a more hospitable environment. This property was owned by a local DA - bad move on BGs part.
Our local PD here are very visible in smaller strip centers when businesses are closing or during times when the take-out restaurants are busy. It has really lessened problems here.