Buying a fresh of the track TB is a very different experience than a leased tb that has had all the time and training done to bring them around and turn them from fresh on the muscle racehorses to an amateur friendly riding horse. Please realize that it is a lot of work and often involves $, blood,tears and a lot of sweat equity.
Many racehorses have some serious wear and tear on their bodies so make sure you do a good PPE to make sure the horse will be able to hold up for what you want them to do in their second career.
I have had many friends get way over their heads either overhorsed or with an injured horse after buying straight from the track if they didn't really pay attention.
New Vocations is a good program that does some of the vetting out and temperament testing, but you still are getting a very green horse. So go in with your eyes wide open! Good luck!