Since I read your introduction, I must say that, while your goals are admirable, it is really not wise to buy a young horse (just because it's cheaper) when you don't have any experience with horses yourself. Horses are very much unlike any other animal people sometimes choose as pets, their health issues are different, their training is different, their keeping is different and their behavior/psychology is different. Although learning from experience is a fun thing to do, when it comes to horses, it can very quickly turn into a living hell when you come across a situation that cannot be solved just by trying.
I strongly suggest that, before you get your own horse, you should spend at least a year with a good trainer, learning both horse care and riding. If you decide to get your own horse sooner, you should at least at first keep him at a reputable boarding barn and get an older, seasoned horse.
A young horse is very quick to learn bad and dangerous habits, which you, lacking experience, won't be able to address as needed, and will put both yourself and your horse at a risk.
Good luck and be safe! Getting into horses is a wonderful adventure, when you start off with the right guidance. :)
I have come a long way, to surrender my shadow to the shadow of my horse.