I like the fact that he's been ridden outside. He looks calm with the kid that's riding him. And I can barely make out the bit, but it doesn't look like it has a long shank, which might indicate some control issues.
Obviously you'd have to ride him before even thinking of buying him, though.
I'm not thrilled about the 3rd one. Something tells me that she's selling him for a reason other than, "Well, he had the most potential of three horses I own." His eyes look like he's spooky too. Also, she says that he's been "exposed to a lot" because the barn that he's at hosts shows and rodeos. She didn't specifically say that he rode in those things. Also, I don't like it when people post pictures of a horse and they aren't ON said horse.
I'm not gettin' on that thing until you prove that it's broke!