As a proprietor I have seen just about anything and everything when cleaning out places once a occupant has vacated.
I have had to update flooring harmd by pets, redone plumbing that was plugged or harmd by irresponsible people, and even had to spend money for industrial cleaning in some cases. This last issue almost had me giving up on they whole process entirely. Sure, I was able to keep the security deposit, but, that didn’t come close to covering the cost involved in repairing the HVAC system. Not only did I have to have the ductwork cleaned due to the stash of drugs my buddy and I found tucked in the vents, I had to have the device repaired because they had kept it running non stop with a humidifier set up to help grow the plants in the basement. They had jammed off numerous of the air vents with cardboard so that the heat could be directed to the growing section more easily. This had causes a build up of debris at the opening of the vents that can only be described as gross. I had to make sure that the HVAC system was scrub and safe before I could rent the device to anyone else. I have changed my rental agreement to include annnual inspections because I want to ensure that occupants are not damaging my proberty like that again in the future. I feel it solves the mystery as to why the previous people never complained about anything or asked me to repair anything. They didn’t want me to see what was really going on in the apartment. I won’t make that mistake again.