I had a neighbor who had a Morgan gelding. He made an awsome hunt horse, but had had a bad experience with driving (what they originally wanted him for), so that was out of the question. He'd freak out even SEEING a cart.
Well, she advertised him as "broke to drive". Not true, at all.
Same neighbor had an Arab gelding that made a wonderful trail horse, but as a show horse he just couldn't do it. Not that he wasn't pretty and didn't have the movement, but he did NOT like being in the arena. It didn't matter what you did, you could lunge him til he was dripping sweat and tired, he would still buck and rear and carry on in the arena. And it wasn't ill-fitting tack or pain; take him out of the arena, he was a perfect gentleman. It was all in his head. To top it off, he was NOT a kids horse.
She sold him to a couple who's 13 year old daughter (young, but she had been riding her whole life: Thank God, it could have turned out worse otherwise) planned on doing show jumping with him. The girl ended up selling him after being thrown and breaking her leg. Among the million other problems she had with him anytime she took him into the arena.
This wasn't exactly an attempt to sell a horse, but it kinda fits.
The guy who boards my horse for me had a 4 year old Arab. She's extremely sweet, I've never seen her do anything mean. He sold her to a lady who's "trainer" is a kid I would guess around 17 years old. They had the mare for maybe a month, called the orignail owner up and said the mare is mean, they don't want her. "She kicks, she bites, she bucks whenever you get on her, she's just not a safe horse". Not gonna work when she's been bought for a 12 year old girl. So we got her back, I got on her the next day. She didn't do a thing. She walked for me, trotted for me, cantered for me, turned perfectly, everything I wanted. Other people have ridden her since, she hasn't done a mean thing. I honestly don't think that horse has a mean bone in her body, but the kid training was just an idiot. I saw him ride a little later (he's my boyfriends neighbor, so I see him all the time), and with the way that kid rides, I can understand why the horse didn't cooperate. Jerking constantly, spurring consantly, even when the horse is doing what he wants.