Firstly, she said TB guys not OTTB.
If you have reservations about it, it's likely not a good idea. While you have the assistance of your Aunt (which is a huge plus!) there may be issues that arise when she is not there to help you. Also, a young horse can be quick to learn who is boss - your Aunt may put the horse in his place but you may not and this could create more problems.
Go with your gut feeling - it's normally right.
Stop for a minute, open your mind, learn. You may not agree with what I say, I may not agree with what you say but we will both learn something new.