I'm pretty sure I could research and find the correct/safe/legal (as you all seem to put it) manner in which to remove/dispose of these potentially hazardous materials along with the right chemical/cleaning agent to pressure wash any meth residue from the structure's skeleton...With all that said, it doesn't seem like much fun and I think I will pass on this deal, and by the way I would be giving the same advice as everyone here if some anonymous "investor" asked about this online... so I appreciate the words of wisdom.The thing that isn't clear to me is: would I, or would I not be breaking the law by continuing with my "plan"?

If I sold him the building on a land contract for $250k, which is exactly what I have in it, on a 15 year payout, am I correct that the sale would result in a wash, no earnings to be taxed on, and the only taxes I will pay will be on the interest portion of the monthly payments for the next 15 years.  

Unless you pay cash for this deal...I can tell you that this deal will be close to a wash.  

You see, I currently wash dishes for a local restaurant chain during the day, bring in barely 1k per month in income (after taxes), a little over half of which goes toward living expenses, and use a bicycle and the local transit system to commute around town since I don't own a car.

If friends are not willing to let you show the place and leave a mess behind, then at that point you should simply reconsider your generosity to someone who doesn't have the same respect and consideration for you.One hand washes the other.

We haven't had a formal sit down , but all he kept saying was he wants out.

Not only does it make the house stink, but there's a lot of extra labor involved (i.e. washing/scrubbing walls) whenever it's time to repaint. 

Many landlords have reported that dog washing stations are the most used amenity in their building.

You need to have an attorney with lots of experience doing these to assist you on your first one, then you can wash, rinse, repeat.  

A good power wash and coat of paint on the outside goes a long way too.You can get estimates from many mobile home-specific contractors that understand these needs if you are not going to do it yourself.Basic repairs on a decent old home can run between $2,500 to $15,000 depending on how bad of shape it's in.