How about someone under 21 having a credit card or drinking alcohol?

If there are a lot of neglected yards, the area is full of either renters or alcoholics.

Not to scare you, but I did share a post here of a tenant that literally hacked his landlord when she went to address something with him after she had already indicated eviction proceedings.The landlord ended up in ICU and I did not follow the story enough to know if she lived.The article indicated that even if she lived, she would be left with major brain damage.Once eviction papers are served or termination of tenancy communicated, I would be very careful about going around said tenant as emotions are high and worse where drugs/alcohol is involved.I would for the most part keep away and handle this per the advise of your attorney.Did an eviction once of inherited tenants that a year and a half later, continued to challenge my policies and damage the unit, and it was tough, but seems that eviction (at least once especially with inherited tenants) is just the rite of passage most landlords have to go through.Not saying you will, but as @Marcia Maynard says, please be safe.

@Karen Margrave crushing college debt, delayed adult decision making, chronic alcohol abuse, pushed political agendas.

The only way it could have been worse would been if it had taken an HP Lovecraft "The Rats In the Wall" sort of direction.Could you have found a perennially broke alcoholic or two to handle the roach corpse cleanup?

In March Chris Ward headlined the San Diego Tourism Authority's annual meeting, a free event at the Dream Theater at Sea World that was fully catered with alcohol and had porcupines and other animals being brought out at the cocktail party following the ceremony.

How can alcohol be legal and marijuana illegal?

Also she left her parents house when she was 15 because they were abusive  alcoholics. 

In my opinion, I've found that the most important piece of owning an alcohol and drug recovery home is the manager.

Starting at 1/2 through first allows the alcohol to loosen them up but not enough to get questionable judgment.