Even the dangerous molds are manageable unless you already have respiratory problems.Ensure the ventilation fan sucks air out and vents into the outdoors, not the attic space.Train the tenants how to kill/clean the mold with a simple bleach solution and spray bottle.

I recently went in the unit a discovered water from shower head sprays all over walls and ceiling when on.

The ceiling beams was spray painted black.There was an odor still coming into the house so it was suggested that we had a rodent issues and to remove all the old fiberglass insulation in the attic and put cellulose which is coated in borax to deter animals and help insulate the house.

They buff out the old surfaces and spray on the new coating.

Is anyone using bed bug spray on their mattresses after a guest checks out?

I have had  them take stuff, but to me the worse was when they spray painted the kitchen cabinets and smashed random sides of the cabinet, cracked the glass on the stove, spray painted the inside of the frig and oven, cracked the blocks of the patio and left the spilt alcoholic beverages and ladies underwear all over the hardwood floors. 

Then put down new flooring.If the cat is a sprayer, they could spray up against the walls.

(Actually going to pull the new carpet back along the shared wall and spray foam any gaps under baseboard).I have not confronted the neighbors yet as it is in my experience that smokers in general (especially dedicated ones as they clearly are) do not particularly care and it is unlikely that they would stop anyway.

@Leo Varghese  Spray it with bleach, put some gloves on and if possible wrap a garbage bag over it when you carry it out.

Mother-of-Two has refused to use any of the rent money she deposited into the jar in the kitchen cupboard at.