missing furniture in upper unit and the huge scratches in wall 18' up in stairwell.

So, they leave all their furniture, and sublet it as furnished with my permission.I got to where I did not want parents as co-signers. 

They let it wander loose in the house and it dug or chewed the carpet under the furniture.

Then, you have to deal with removing furniture and storing it.

Sometimes you give a little, yes, for example I had one tenant recently ask if we could add 2 plugs in the garage at his expense because he is getting into building small furniture.

I created COGS accounts to match the line items on IRS form 8825 to keep it simple but most of my transactions so far don’t seem to align with them (things like tool purchases, furniture and light fixtures, and a wall divider capital project).4. ...

We had to remove baseboards, pull up carpet, replace boxsprings, disassemble furniture and put it out in the shed (at -25C for a week).By the time we were done three treatments of the entire lower unit in the building and inspections of the upper unit to ensure they had not spread that far and had replaced mattresses and boxsprings -  we had spoiled the better part of $5K.Since it was a rooming house, we had to act quickly and assume the costs - the tenant skipped anyway (and has no money).  

They had rugs, toys or furniture covering up every stain.

When we were done at the notary and finished the purchase, we were able to obtain the license and start the works (it was a big commercial old furniture shop where we created 14 tourist apartments). 

This shocked me, as normally if I list something for sale on the internet (like say an old piece of furniture for sale) it seems like the ratio of scammers and weirdos to legitimate buyers is about 10 to 1, that did not appear to be the case for the rental which was a nice surprise ...