Stormie, my momma had a tenant like that once. Problem was they also were one of those weird folks who decide to hoard *dogs*. Aside from the den of garbage, SPCA removed some large number of setters from the place, in terrible condition.
Now the bad news, the parts of the place that weren't ruined, we had to live in. It was our house that was temporarily rented out and we had to return to it.
It was my job to clean the dead rats up after our homemade rat poison+oats mixture did its job.
(Ma, it has been an interesting life so far and I do believe I am far richer for having gone through all that stuff.)