We checked it out, and loved everything but it's need for smoker remediation.

Considerations I've found so far include: various layers of outdated insulation (mid-80's fiberglass stuff laid over old vermiculite), 1x2's nailed together to create 2x4's (but still relatively sound structure for the age), asbestos siding (needs a powerwashing and I've found it's totally OK, until it's time to rip it off or demoed), 1" galvanized metal water main is very old, electrical wiring that is visible is a hodge podge mess, there's an old gas pump on the site (not sure if tanks are still buried), real bad mold in bathroom, at least 3 layers to the foundation (that looks solid still), ugly old wallpaper, cigarette smoke smell, kitchen is a complete gut and remodel, nearly the whole home is.  

Previous owner was a heavy smoker and left behind all furniture and personal staff(that was part of the deal).

Before renting out a unit I have to make sure by asking if anyone smokes cigarettes, marijuana, hookah, etc.

Smokers are not a protected class.

I've had two occasions where the reference they listed told me not to rent to them because they were violent, late payers, or too needy.Not doing a criminal, credit, background check, which might have revealed criminal or credit problemsBeing slow to evict (mentioned by others)Believing their sob storiesAccepting partial paymentsFailing to document every conversation or interactionNot walking through the property to make sure they're taking care of it (I now walk through every 9 months so I can see problems in different seasons)We've found crack pipes and other paraphernalia after they moved outWe've discovered piles and piles of trash (some bagged, some not) in closets, basements, sheds when trash cans and pickup service are included in their rent - all they had to do was carry it out, at no cost to themWe've Found smokers, pets, extra peopleOverall, I've had great success as a property investor. 

You can rent machines that put out near lethal doses of ozone that use a timer that you set, vacate and then come back hours after the ozone disperses.We've used ozone to get rid of bed bugs, mold, smoke damage, cigarette & weed odors, etc.Recommend you Google how to get rid of meth contamination, so you understand the process and don't get ripped off!

Metal Building maybe $60k, he wanted to keep renting, he was running some sort of part time cigarette or E Cig business out of. 

Non smoking tenants (smokers often break the rules and sneak a smoke inside) no candles and knowledge of electrical appliances throughout the house hugely diminishes risk. 

They left the unit in very bad shape (holes in walls, cigarette smoke smell, soiling and damage from unauthorized pets, graffiti and intentional damage, unflushed turd and vomit in the toilet, drug paraphernalia and liquor bottles, disgusting furniture and trash left behind, fridge, dishwasher and oven looked like crime scenes, cockroaches in the cabinets, grease down the drain, literally the works).