Savogran 10621 Trisodium Phosphate (TSP) 1LB (16oz)

https://www.amazon.com/Savogran-10621-Trisodium-Phosphate-16oz/dp/B0001GOGQW/ref=sr_1_1?crid=2ETVVOH1C9ID5&dib=eyJ2IjoiMSJ9.YrcbrbLTxHWDiCLPpQXsZIGdV3f0-xIIJ2Q64NEK6i8dfNsOV3y7gS9ADkAhQawIAY6kigiiaiwokr0rdTLx_SDQ-JtSz50XghqmRuEDNItv5eigU6GU0Hw4AKbTZRM1LUDPiBWHOQ5evgTzr3mzr-iCVb6i4mQYfE1Lm3EtXebaKPujiYmH1MYrK832ANWrew7PkkCRoVbiXuHFjKTQbgo6dEm0SS89NkaYbG5pJjwSx8cg2_xcBY4A0j1Yz2A3OGb4N8mdA5TkzjZYEjApy9k7I4veaHuGSBjyyv0-hPA.r_emWjSsfUYuWNPB2fv12Y776G3IHtnBTGI21HmINGw&dib_tag=se&keywords=tsp&qid=1782134703&sprefix=tsp+%2Caps%2C462&sr=8-1 you're welcome

Obviously rip out carpets and pad. If there's concrete (garage, closed porch) affected use TSP: https://www.amazon.com/dp/B0001GOGQW It breaks down the uric acid crystals embedded in the concrete. For everywhere including on the concrete after TSP, use Rocco & Roxie: https://www.amazon.com/dp/B00J9MYM5O I once bought a home where your eyes immediately burned when entering the garage because the former owners had kept what smelled like 90 cats in the garage without a litter box. These two products made it so you couldn't even tell it had ever been an issue. It was a miracle. My oldest daughter regularly rescues dogs, and of course regularly has issues with that as well. Rocco's gets used after every "accident" and her house smells great. I'll add: despite others saying "replace the subfloor" I'd only consider it for areas where the subfloor is soft. If solid, I'd clean it with the TSP which is good before priming, and also use Rocco's on it. Then prime it before having new carpet installed. If the subfloor is soft anywhere or chipping away / dissolving, then replace that sheet for sure. Scratches on drywall are generally easy to repair, but before that I'd clean it with Rocco's as well, at least the lower 2 to 4 feet of it. Probably bring in some fans to help dry everything faster. Once dry and smelling nice, patch drywall, prime with a good primer and paint away. DIY it will be some work for sure, and outsourcing it might be expensive and give mixed results depending on who you hire. But as someone who has bought distressed properties before I wouldn't stress over this one I'd just price the work into it.