Nothing. You have to do it right or walk away. Doing anything less shifts the burden of responsibility on you.
As long as everyone is on the same page then maybe you will be fine but most of the time "people" expect a squirt of this or that to remove gallons of urine soaked into all those materials for years.
It just can't happen, not even with a "magic box" Ozone generator. Its hard work to correct that damage and its going to be expensive, anything less is just a band aid on a gaping wound.
I think it depends on the degree of contamination whether it can be treated satisfactorily or not without restoration.
You can treat many mid level urine jobs with chems and/or ozone. I've done it many times, there are plenty of different chemicals from many different suppliers for this purpose.
To say the only way to treat urine contamination is to go nuclear and start ripping up carpet and pad is somewhat extreme, especially if you are dealing with rental property management that needs to turn over a unit fast and cheap.
Will the odor come back? Probably, if the humidity levels aren't controlled.
Years ago my sister rented a house that had a pretty bad doggy urine and body odor issue. I chemically treated it and killed the remaining odor with Ozone, it was fine until I cleaned it for her again a year later. The odor returned as soon as I started cleaning the carpet, ozone it again, no more odor.