My TB is an unbroken 2yo, intended for performance.
I am currently in the process of mouthing her (this requires FEEL and TIMING, two things that cannot be taught), and getting her used to the saddle. She won't have any weight on her back for at least another year yet, possibly two depending on physical and mental maturity. Her sire supposedly throws late maturers a lot, and she's quite a big girl already, so I'm figuring, better safe than sorry.
At the moment I am on the fence about whether I will send her to a professional or not. At this stage I have absolutely no interest in being the first person on her back, but that's because she is capable of the most terrifying rears when she's pushed too far outside her comfort zone, and when the time comes she may well be less explosive.
I don't believe you have to be a perfect rider to break in a horse, but you DO need to have very good timing, feel, and knowledge - and you have to be EFFECTIVE. If you haven't worked with young greenbroke horses before, don't start them from scratch yourself. It's a recipe for disaster. Generally speaking, if you pay someone else to break them for you because you don't know enough, you also don't know enough to work with them and educate them as green broke horses, so you may find you have to have them professionally trained a lot longer, or at the very least have regular sessions with a reputable trainer who is willing to get on and help you out if you or the horse are just not getting it.
The last greenie I had was a 7yo Welsh... he was an awesome pony and had established basics on the flat, I cured him of his bucking issue and got him consistent with his canter leads.. taught him to jump, then outgrew him.
The one before that was a 5yo Standardbred and he was pretty much what you would get from a professional trainer - he had been under saddle for 7 weeks and was reasonably consistent walk/trot/canter with very basic leg yield and was beginning to carry himself round for a few strides at a time. I ruined him completely and by the time I had to have him put down, he had LESS education than when I first got him. He was reasonably consistent w/t/c but had no leg yield and no self-carriage... AFTER a lot of work rebuilding the relationship!
Something you will need to know is that you are GOING TO ruin the first two horses you train, at the very least, and many people ruin plenty of others besides. That prospect terrifies me beyond belief, because I've only ruined one, and my filly is damaged enough as it is.
You sound young. My advice? Your first breaker SHOULD NOT EVER be a TB. Some bloodlines are easier than others, but I've yet to hear of a TB that would be suitable as a first breaker for a young person. Some of them are incredibly difficult - I know of one bloodline that all the breakers hate because they all buck something chronic, resist all training, and put the breaker in danger. Some of them aren't so bad, I think mine is one of the "easy" ones going on what she's given me so far... but some of them are purely nightmarish.
Leaving them until 4 is often a good idea. That's when they grow a brain and (usually) learn some self-preservation. A 4yo is less likely to kill itself and you running into a tree or a wall than a 2yo.
A CLEAN SLATE FOR THE FUTURE