Even though the pictures aren't great for a really fair conformation evaluation and this mare obviously would look better with some weight and conditioning, I personally don't see a " diamond in the rough ". I think she's got a very plain head, weak-looking lower legs and steep croup. I would be suspect, too, of the hoof care she's received with her current owner. The ad you quoted says nothing about her ability to gait...usually one of the
first things a gaited horse seller brags about.

She may be just fine as a trail horse, but not at that price.