If urine it has probably gone through the carpet into the flooring.
When we bought our current house 18 years ago the former owner had a
cat that had peed a lot in certain places. We removed the baseboard in
the kitchen and found thick dried urine deposits. We replaced the
baseboards and found it had gone down covering the joists in the
basement ceiling. We removed the basement drywall ceiling and painted
the affected areas with KILZ to seal in the odor. Problem solved.
Don't underestimate the work involved. Presumably you are getting this
house for a good price.
Remove all carpet and try to get an ultraviolet light that will show
where the urine concentrations are.