However the very nature of your question seems to indicate that what you would like to do contravenes the purpose of the statute which likely means the Service would go the extra mile to enforce the letter of statute against you, and if that were insufficient invoke substance over form anti abuse provisions to prevent you from accomplishing what you desire.

And that is why easing over long time can be a dangerous move...I think we are at that point already where nothing is worth doing because of the rates...

I just advertise my rentals with "no dangerous dog breeds".

Occasional flaking off of some substance that looks like dried mildew when switching between heat and cool.

This moral dilemma mentality is a dangerous slippery slope that leads to extremely biased and unfair regulations like we now have in Portland,  where if I need to have a tenant leave my person property so I can do an extensive remodel of the unit, (or because I have just had it with a bad tenant),   I have to give them 90 days notice and pay them $3500 "moving assistance".    

But starting to flip in the current market today is much more dangerous than it was 3-4 years ago, especially if you don't have experience.  

Tenant understands that any damages caused by smoking any substance will be considered damage.

I know of the dangers.  

These things do happen I am afraid.Agreed 100% I would focus more on substance then upgrades that a home owner would care more about

I realize the rules are easy to get around, as when an adult buys a controlled substance for an underage accomplice.