(this was my estimate with input from the realtor who apparently does demo on the side)- All new flooring (combination of carpet, laminate, vinyl)- All new interior doors and hardware (6 panel hollow)- New (matching) light fixtures- Most or all new interior trim- New counter tops with modification to remove partial wall and add breakfast bar to open space between kitchen and dining room- Refinish existing cabinets- New bathroom fixtures (vanity, sink, toilet, tub) in both bathrooms- Likely sub-floor repair due to the significant amount of pet damageThe major areas that I didn't look closely at (because of the pile of junk in the way) but would certainly need to if I was considering this include the mechanicals (AC compressor appeared original), septic system, well, a closer look at the roof, and a closer look at the deck. 

I have seen it where tenants have stuffed the cabinet below the sink full of items, to the point that it has damaged the piping. 

I buy mine by the hundreds and I get free steaks and shipping.

A couple of decent books and a hundred or so hours on BiggerPockets, CreditBoards,  HUD.gov, and her state's housing finance authority's website will result in a far more complete education for a tiny fraction of the cost.

I did everything from drywall repair, to tile, to kitchen cabinets to sanding staining floors.

A couple hundred bucks?

It should only be a few hundred dollars. 

They mentioned that they would pay me a couple hundred dollars, but if I put it under contract with her and assigned it to my buyer I know could do at least a couple thousand and there still be plenty of room left for the investor purchasing the property.

Do you just figure a flat figure that covers a traditional renovation (i.e. new floors, paint, appliances, cabinets, counters, baths etc.)? 

Depending on what exactly the issue is, a roofer could add venting (maybe a few hundred dollars) or you might just get a spray foam insulation company insulate the attic (a few thousand).