Look at the topography and terrain to determine how.Evaluate fundamental infrastructure and service availability, as well as expose examples like wetlands and flood zones, protected lands, hazardous chemicals etc.

Everything I read online says DO NOT use exterior stain on the interior due to the fact it gives off harmful chemicals. 

I'm debating if to start with them because I've been trying to do my own research but I'm not finding anything with substance to actual help me start. 

He may have a substance abuse issue but I have no proof of that and he is unemployed I believe. 

You will get efficiencies of scale with chemicals and service calls.

Painting with Kiltz or Zinsser BIN will seal the smell, stain and chemicals for a while, but they may eventually come back.  

We washed the concrete with a garden hose and chemicals.

I joined bigger pockets a while back but had to focus on paying my way through school and passing a dual major in Chemical Engineering and Paper Science Engineering.

Familiarize yourself with the Fair Housing Act, which prohibits discrimination against people with disabilities, including those recovering from substance abuse.

I don't allow tenants to smoke any substance, or vape, inside their units, garages, or outbuildings.