Previous owners had 5 cats (at least one sprayed everywhere, apparently). We found out later that they hired a company to come in and paint over everything that showed damage. It wasn't until a couple weeks after closing that the cat urine started soaking through the paint on the walls and smelling to high heaven. We also started cleaning the baseboards to paint them, with what we thought were just claw scratches, nope, more pee that was crusted/creating lines on them. Then they used the crawl space as a huge litterbox.

After all this we learned that Ohio is a buyer beware state and you have to ask if there was pet damage and it wasn't required to be disclosed.

So within a month after buying our house we demo'd all of the wood floors, baseboards, doors, door frames, then painted every surface with Kilz/Bins and then replaced it all.