They even work with us where, for example, on one turnover last year we came in town and did what we wanted (pressure washed house, painted outdoor trim, stained decks, fixed fence, etc.), then they finished it up when we were done.  

I went and washed my hands.

I guarantee you, depending on the tenant, the invoice will be higher the there deposit, let them challenge it, they will lose every time.As per the urine smell, I bought a run down 8 unit apartment building, each unit was so bad the 1st thing that burned where your eyes, the 2nd was your lungs from the smell, each and every unit.Pull the carpet and padding, then go take a shower, its grouse, then wash walls with heavy bleach water, then pour and scrub heavy bleach water in to sub floor until it is soaked. open windows let dry and air out for a few days.

But in March the upstairs tenant calls us again and says that her washing machine is not working.

Or perhaps A- (we still haven't replaced the windows, will be A after that).

I understand the posts saying to simply cut ties and wash your hands of the mess and move on. 

Treat it like a washing machine.

Then use a clean product or method targeted for that type of odor.We clean all hard surfaces with a cleanser/degreaser, then a vinegar wash, and finish off with a disinfectant. 

If the aweful smell is lowing down my unit turnover and I need to fix it anyway, then I would get on it pretty quickly. 

While it's not close to the Univ of Wash, it wasn't far, and it was less expensive for the students to live in that apt than to live closer to the University.