How long will it take to train a horse for dressage/jumping?

I plan to get my horse started next week, he is 12, a former racehorse, but very smart and level headed. The trainer I have chosen told me my horse would be needing 3-4 days of training per week and 5 days per week in the beginning. I know nothing of what is going to be happening or even what questions I should be asking. The trainer is more than qualified and states that perhaps in a few months we might aim for a little beginner show. Our goal is to ultimatley sell the horse as a dressage or jumper or both. I guess the horse will dictate on many of my questions as I do understand that everyhorse is different.