Renters do wacky things sometimes, then refuse to own up. How much money I keep is directly proportional to how much work/annoyance I have to do/put up with to make the place look like it was when you moved in.

Example, last renter ran speaker wires using some kind of sticky tape along the baseboards that left lots of glue residue on the wood floors. It took me experimenting with 3-4 solvents and a lot of elbow grease to get that stuff off. Thus, I dinged him big for it.

You can't generally hire decent janitorial help that gives a damn and have to do it yourself. Giving a damn costs my time so you get to pay my consulting rates when you do stupid stuff that I have to fix myself.

He could have gotten his money back by cleaning that stuff up himself.

I've only kept a whole deposit once (and I get a big deposit) and that was for a psycho I evicted after only two months. It cost pretty much all of it to fix the place up, plus lost revenue for having down time, lawyer fees, asshole tax, etc...