I've been in some nasty homes over the years, two hoarding sisters where I had to walk through a path throughout the house, but the worst was one in Springfield. An elderly couple hoarded cats, they had over 50 of them and the wife was hospitalized, soon thereafter the husband was too. They were both in for a couple months while the cats were alone in the house. Eventually the authorities took the cats away. When I was there the wife had passed but the husband was alive and living in the house. You have no idea what over 50 cats will do in a house for weeks without being fed. The smell almost knocked me out and the cat piss curled the Formica countertops. They also pissed along the baseboards which were bubbled up. The old man was living in those conditions.
A year later I got an order to appraise the house again, by this time the old man had passed, and a contractor purchased the house and gutted it and renovated it, it was in good shape this time.