it’s obvious their pets handled the moving process poorly and have urinated in every room with carpet
Cleaning up pet urine can be really expensive depending on how bad it is. If it’s not just a few spots here and there, seriously consider ripping out all of the carpet and padding and living on the floor boards until you can get new flooring.
You should buy a black light. Nothing expensive, $20 or so. And shine it on everything with the lights off, urine glows. As a side note, anyone looking to buy a house, or even get a new rental should get a black light.
Steam cleaning urine is a bad idea. The heat will cause it to bind to the carpet even better and make it even harder to get rid of.