I think the most important thing is to be honest when selling a horse. If there are issues, then be up front about them.. A few years ago, we went to look at a "fantastic" barrel mare. Big, beautiful, well trained, yadda yadda. We drove 8 hours one way in the wind to see this mare she sounded that good. Saw lots of photos and talked to the owners time and time again, they knew we were driving 8 hours one way to see her.
We drove up and I almost got right back in my truck, the horse was a big huge ugly mare, feet the size of dinner plates, looked older than the 12 years she was supposed to be. But, decided to give them a chance anyway. They saddled her up and the guy says" I wanted to be completely honest with you, she is a bit "light in the front".. Of course I work for a vet and have been around horses for ages, so say" ummm, that would mean what exactly?". He says, well she moves stiff, but if you Bute her before every run, she will be fine.... He untied this mare and she could barely turn around she was so painful.... We immediately started to leave and I asked one simple question" you couldnt have mentioned this before we drove 8 hours and he said" well, she works out of it after she is warmed up and I thought you would want to buy her since you drove so far".... I was lived and we drove away.
So, I want honesty in a person about their horse, good and bad and then let me decide if I can accept the bad with the good.