They leave trash everywhere and the odor of cigarettes and marijuana streams from their unit.

I would then give him an estimate of professional cleaning costs and odor removal.

I've also been told there are some special paints that can be used to eliminate any lingering smoke odors in the framing of the house.

Well I look at the faucet and it needs to be replaced , but I tell the tenant that I will be back in 4 hours , clean the place , I cant work with the odor of garbage and a sink that is growing a science experiment .  

Looking to get rid of major odor in house. 

Sounds silly but odors - even potpourri -matter to some people whether they know it or not.

Public water/sewer.Main Floor and 2nd floor have no odor, no mold.  

When looking at investment property, pet odors smell like money.I bought one of these a few years back and was prepared for chemical warfare. 

Basement was gutted and drywall and ceiling tiles were added and painted.The garage had a strange odor and the floor was sticky from old carpet so the floors were epoxy painted.

Still in due diligence and have alerted buyers agent that we will be going back to seller with a discount on the offer to take into account the odor remediation.