Especially when that person has your high value asset in their possession, tying up cash, or potentially neglecting, or even harming the asset.  

Things like old ovens, random chemical waste, excess trash left behind by a tenant, etc.I used to drive a sedan and I was able to make that work, but having a truck is just a bit easier, in my opinion.

@Bret Allen We provide the house pest-free and will re-treat if reported in the first 30 days.Our lease has had the term "any additional or periodic pest control is the responsibility of the tenant" for at least the 11 years I've been here, and it has been vetted by our attorney.I understand your opinion may differ, but I would rather have a tenant raise the issue of being responsible for their own cockroach problem (we do SFH, so neighbors don't play in) than being named in a suit for damages because somebody had a fatal reaction to our pest control vendor's choice of chemicals. 

Burden of proof is on them - they have to prove you did (or didn't do) something that caused "harm". 4.

Before that it was lead paint.There are VERY FEW species of mold which are relatively rare that are harmful. 

We hired a pest company that used a new chemical treatment at the time, which would have been about 2013. 

I'd find out exactly what you can request from her, and if she provides it, you're likely stuck allowing it unless you can prove it is harmful, like you'd lose your insurance or something similar.  

hi. i am a landlord but i do not manage a 60 unit building. i agree with everyone, get a property management company to run things for you. i do a lot of work for a property management company here in the buffalo, ny area as a handyman. quite often, we handymen know of better and faster ways to get the parts you need than doing it on your own. that being said, a/c units have to have a licensed professional work on them anyway, but knowing how to get the parts faster is always a good thing. as far as the tenant threatening the police, lol, they won't even get involved. they have better things to do than worry about some joker sweating a little bit. you dropped off a fan, the tenant refuses to open the windows, which is on him, so he, himself is causing himself and his family more harm than you are. if he is worried about the high crime issue being on the second floor, lol, criminals work as little as they can. they sure as hell are not gonna scale the side of a building like spiderman just to rob this guys place of residence; unless he has a bag of money or gold stashed in the place, in which case he probably wouldn't have been late with the rent 6 times. my advice, continue down the path you are on. hire a property management company, boot this dumbass out the door when his lease expires and let him become someone elses problem. good luck

The prognosis from the cleaning crew was that the chemicals they would need to use to clean it, probably wouldn't make it very safe as a fridge for food afterwards.

Nothing is offered to cause harm to anyone, but may be useful in your situation.