First hubby and I had a couple rentals. Had a renter once that lived like that...you poor thing. He was some kind of mechanic and never cleaned the tub or toilet in the two years he lived in the place plus he smoked. The stove had to be thrown out...you could not clean it. I got sick from the chemicals when I first tried. It would have taken a commercial crew with industrial products to clean it.
The house was about 800-900SF. We gutted the house and started from scratch rather than attempt to clean it. Of course, he never paid the last couple months rent and he acted like it was no big deal when you talked to him.
Never will I own a rental again.
I am not a super duper neat housekeeper but it is TRULY amazing how some people live.