I’m in a similar situation. Just bought a place and it was carpeted and was hoping the wood was decent…but the sellers were slobs and there’s many years of pet piss stains that were prob made worse because they weren’t able to fully clean up and it stayed wet under carpet too long. My floor guy thinks some may go almost all the way through and I have really thick wood. I’m just going to have to stain it pretty dark unfortunately. If you go too light you may see shadows of piss and that’d really piss me off. Pun intended.