After de-catting and de-dogging several units from the odor, fleas, hair and damage caused from urine, feces, scratching, digging.

This is part of the learning experience.As a former carpet cleaner if it is cat urinating forget about it and you will %99 of the time have to replace carpet, pad and possibly tack strip and base trim not too mention sealing cement floors etc.Dog urine can be easier to deal with depending on dog.

Cat urine horror stories,, are you prepared to replace dry wall up from the floors at least 2 feet and all the base trim,, carpeting, and probably sub floor...

He thinks it is dog urine. 

COE last week, rain this week, new flip is flooding, the ceilings are urinating all over the "plush carpet", the textured walls are now 99% wet, and I have a crying new millennial buyer soaking tears in IPA's by the growler full! 

It makes a great filler prior to staining.A word of caution on dark stain...Our first house had urine stains(very dark, cannot remove without replacing)  we decided to go back with a chocolate stain.  

But if the flooring itself is in disrepair (bad planks, wide gaps between planks, deep water or pet urine stains, holes, etc), usually it's best to just start with fresh flooring.  500sft isn't a huge area to replace.

Construction, construction, construction...This will be one of the biggest hurtles for the new flipper. 

The bathroom floor is so soaked with urine that the entire subfloor needs to be pulled up and replaced, and a new floor laid down.The entire apartment is a mess, and full of old clothes and trash.It is obviously not in showable condition.So my question is this - since the verbal agreement we made was broken (not moving out the 15th, not providing pictures, and not leaving the place clean) do the terms of the original lease remain in effect?

The smell of cat urine is difficult to get rid of and could be another reason it's so inexpensive.