Well he has quite a short croup and undermuscled hip. His neck ties in a little low for my liking also. Hard to tell much about his legs with the way he is standing in the picture.
Temperament is a big factor in my books though and he looks to be sweet. If he rides well then that is a bonus. He doesn't look to be in very good condition, not underweight as such but undermuscled and his coat is very dull, both of which will improve with a good feed regime, work and of course, time. I wouldn't be wanting to pay very much for him in his current state.
All horses deserve, at least once in their lives, to be loved by a little girl.