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

From 1 TIM 6:9-10:Those who want to get rich fall into temptation and a trap and into many foolish and harmful desires that plunge people into ruin and destruction.

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

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

As long as you are not betting on property appreciation and more for cash flow, and you have done a full due diligence on the real estate asset, I think there is no harm in expanding your portfolio of investments to real estate. 

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

I concluded at that point he was likely to be more flash than substance.

I don't know Nebraska law, but I think it's a fairly universal concept that whoever provided the alcohol is next in line of liability after the person who imbibed and later caused harm to someone or something.

Keep your HDTV out of harms way. 

They estimated and quoted full restoration of the fire damage which included soot cleanup, odor removal, clean air filtration (out of fear there may be something harmful in the air from the items that burned), and floor replacement.