Pet urine, fleas, insects of all sorts, plumbing in disorder, roof leaking - and people are still living there; to those people still living in such conditions, they probably think that is "livable".

He said the whole back of the carpeting had urine stains and there was some dampness still on the subfloors in the stairway.

That's Bull and makes wholesalers look slimey.Okay, So some one goes on here and posts some good points about Birddogging, Assigning, and Wholesaling and the curmudgeons drop trou and urinate on the dreams of the aspiring wouldbe wannabe investor. 

I have refinished hardwood in a rental, but only because it was the only way that worked to cover animal urine smell.

There was a really bad cat urine odor in the unit that will simply not go away.  

These are going to be your biggest hurtles.

Areas damaged by pet urine must be painted/stained to remove odors.9.

There was urine and poop on the pads and the floor.  

In my case the tenants have allowed their dog to ruin my wood floors by urinating and vomiting on it for an extended period of time without making any effort to repair or stop the damage.

I've used a product called OdorXit on pet urine and was happy with the results.