Well geez, I've owned a handful of halter horses who made great riding horses...I suppose it's all in the meaning of what type/discipline of riding.
Is he registered, Percheron? Any conformation problems, or do you know why they are selling? The horse market is not as great as it used to be, in fact I get offers for free horses that I don't even have room for. There are a ton of good riding horses out there that are more than reasonably priced...but then again- if we're women, everyone will just have to understand when we find "One-of-those-special" horses lol. Haha!
It's really up to you. If you're looking for a horse to train under saddle it sounds like you've found one. If you are looking to save money, or buy a horse that has already been trained under saddle, there are lots out there.