They urinate and poop all day, the feces attracts fruit flys, it's a mess even when cleaned several times a week.

Especially cat urine.

You would be “urinating into the wind”.  

The property smelled like cat urine throughout the home.

Yeah but that urine is a heck of a lot harder to get out of the flooring : ) 

This is for Cat urine primarily.

Broken window, stained carpet, significant cleaning of things like maggot infested garage, rotting food in warm fridge, urine in corners of carpet. 

You might be a redneck investor if - The strong smell of cate urine in a property for sale makes you smileA property for sale sign cause you to slam on the brakes A tenant threatens to call a lawyer and it bothers you about as much as them calling their chiropractor You can estimate $30K in repairs after a 15 minute walk around You know the comps of every neighborhood within 25 miles of where you liveYou have a contact phone number for every profession needed to buy, remodel or build a houseYou would rather walk a building site than a golf courseYou can lay flooring, hang a ceiling fan, and set a toilet without Google or YouTubeHalf of the employees at Lowes and Home Depot recognize you as a regular Your HVAC guy invites you to the company Thanksgiving lunch 

Since the smell is coming back, it means the source is still there.Pets urine, sewage and dead animals all have different smells.

Cat urine however, is more than just likely to happen and that smell can be impossible to get out without tearing parts of the damn house down - no exaggeration.