Children, mud, pets and urine from pets, children and in some cases the elderly. 

And cat spray/urine is the worst. 

I'm currently at a hurtle and I'm hoping you guys have a answer.

A cat urinating on the carpet for 12 months is going to cause some real damage that could easily cost you more than the security deposit.

Unit 1 turn: renter went M2M, didn't up their rental insurance, 2 huskies from previous owner's lease lived there urinated and destroyed hardwood floors.

It revealed urine soaked OSB and the whole unit smelled of urine.

He was with Spectrum for property management and they just advised him that the tenant that just vacated has done major damage to the property, floors are bare concrete and nicely stained from animal feces and urine, other assorted things in the home are broken/in need of repair.

v=vMq3ux6g4zEBut to be sure, not all dogs bark all day, (some do), and their owners can work with them to stop it--but it's a PITA that doesn't happen with cats. ...until you get a renter who's cat(s) urinate all over the place and you end up having to do some serious remediation just to get the air quality, among other things, back to normal. 

And once it was cleaned out, it still smelled like cat urine.

Just last night (Thursday, August 4th) I came home from a late night at work to find her squatting in the mulched bed in front of the building urinating on the fence in front of Unit 1.