Her back and belly are probably just from lack of use then if she's not ridden much. Just like us, without constant use, the muscles just aren't as strong. If you buy her make sure to take it kinda slow and condition her up to doing longer trail rides, lots of long trotting and hill work will build her muscles back up and I'm betting you will see her topline and belly improve some. The leg injury looks fine really, it's common for them to look that way after a fence accident. It'll always look that way but judging from her stride, she appears square and sound. No head bobbing or pained looked, even stride. She doesn't look aged, just older, but probably from lack of use, and those muscles will tighten up with conditioning.