I get what Adam was saying, i.e. quit wasting time on unproductive behavior, and I would agree with that, but everyone has to have an outlet and something "fun" to do.

As for the eviction purpose, even if it's in your lease (eviction for illegal activites), you'll need to prove "the seriousness" (couple criteria) of the problem and give him notice to correct his behavior. 

I know fighting mice is tough going. especially if behavior encourages it.

Don that is a very tragic event I am sure he has not dealt with fully if he has turned to drugs.You can't just stop doing something.You have to replace it with something else to fill the space.WHITE KNUCKLING and WILL POWER will eventually only lead to failure.My mom worked for years and years at a violence center for women and dealt with people that had issues.You can guide them and try to show the way but at the end of the day it is their choice to want to live or die.Just take in every moment your son is present and in the moment with you and try to cherish those memories.Right now your main goal is to protect the innocent children and take away any bad modeling behavior they are witnessing that can impact them for life.When you kick a habit you have to do something else.Example: Smoking - Bike Riding,Drinking- going to church,drugs-exercise etc.Everyone has stress in their lives and that will never change.As we get older the stress does not go away it just transforms into something else.You might used to have worried about money,then it's your kids,then it's old age,mortality etc.Until your son sees a counselor to deal with these issues and learn coping skills he is going to medicate himself to not feel anything.The first few sessions of therapy is just small talk.The real work begins later on and either people commit and dig in to work on issues or say "Oh I am fine now and get scared and run away".Many people go to their pastor but I feel they are not qualified as a drug abuse specialist or a licensed therapist to help them with situations like that.Don you don't control your son but YOU DO control how you react to what he does and how it impacts your life and family.Maybe you feel guilty for him seeing his mom go through that and enabled him out of guilt to make yourself feel better in the moment.All you can do everyday is work on yourself.If you do that you can have a positive impact on him that can do nothing but help.

It's worth reminding the tenants that thier behavior and habits are likely contributing to the problem.

So I have had good luck or I should say I have been careful, but I have learned that besides the matter of serious financial issues, behavioral issues can provide very real headaches.

I understand your fear of retaliation but if you don't pursue this in one way or another, you condone their behavior.

Learned behavior.  

The great thing about most good people is that if we take action, they will do what they need to do.Nothing wrong with talking to her, preferably while delivering the news that his behavior has terminated the lease (if you have that clause) and that she either needs to qualify for on her own and sign a new lease or move on.

@Steve Garner does your lease make any reference to loud or obnoxious behavior?