So, I would be lending her money to finish the basement, putting some carpet, and doing some interior painting (about 15k so I'd make about 7,500). 

@Jorge Ruiz True, the neighbor house put in very basic materials for their rehab, carpets in the bedroom and basic laminate flooring throughout.

New roof, HVAC, all hard flooring surfaces (no carpet), upgraded kitchen and bathrooms, landscaping and more!

Tile in bathroom, carpet in bedroom/living room, and laminate wood flooring in kitchens.

There was feces on the carpet and wall.

Needs new carpet, some paint and possibly a new AC.

The previous owner had carpet on it, but they removed it and I've been left with plywood only.

In 18-months the damage will be somewhat limited and {hopefully} will not have had the opportunity to permeate the subfloor and structure {though that is a possibility} - you may just get away with a lots of cleaning and replacing finish flooring (like carpets).The longer they stay, the more expensive the repairs will be at move out.

Hi guys,My tenants has been living in the house for over 4 years now wants to upgrade the carpets, install new blinds and repaint a few rooms.She offered to pay for all of it as there is technically no reason to change all of this at this time.

If you're dealing with middle class family rentals I would do things that are necessary:Remove any carpet in bathrooms, Remove any dirty carpet and replace with tile or laminate.