I would say if you know you'll have time to dedicate to it, go for it! Working with and raising a young horse is hard work, but very rewarding!
Pros- you learn Soo much! And young horses are awesome to train cause they are a total blank slate! They're so eager to learn.
Cons- young horses can be alot of work! And they take time and lots of consistentsy. I started out my filly at 2, you said something about starting at 4, either way, you'll have to have the patience to wait a few years 😂 And if it's anything I learned from young horses, it's definitely patience!