(they had a dog and a cat) One of the animals had been urinating so much in one spot that it had soaked all the way through the hardwood AND the subfloor AND into the joists below the floor!

It is perfectly reasonable to require handlers to clean up after their animals that urinate or defecate in the common areas, and to require that no offensive odors emanate from their residence.

Sub floors have areas that are saturated from cat urine.

Ripped up carpet is much much easier to deal with than cat urine.

Unless you can tie the odor to actual damage, such as pet urine in the carpet, you may find yourself on shaky ground.

Cops have also been inside the house and have witnessed signs of extremely unsanitary conditions: pet waste/urine around the house, you get the picture..

I like it because I have 4 boys and, well the other bathroom constantly smells like a urinal!

As long as the cat has a litter box I can't foresee why there would be any urine - and I've read the stories of people trying to remove that ordor or stain.

Some further reading:http://www.biggerpockets.com/forums/67/topics/18091-cat-urinehttp://www.biggerpockets.com/forums/52/topics/48439-cat-urine-hardwood-floorshttp://www.biggerpockets.com/forums/67/topics/48302-dealing-with-pet-urine-in-plywood-subfloorhttp://www.biggerpockets.com/forums/52/topics/32394-cat-pee-in-apartmenthttp://www.biggerpockets.com/forums/67/topics/29131-how-to-remove-the-smell-of-moneyhttp://www.biggerpockets.com/forums/52/topics/37751-third-pethttp://www.biggerpockets.com/forums/311/topics/39475-profitable-house-problems

Urine can ruin them!