Many people think it’s important to let a horse be for the first 2-4 years. While that’s great if they’re in the wild or out in a pasture with the herd, make no mistake. If you’re taking that horse from the stable/stall/pen to the turn out and back, or grooming him, washing, trimming hooves… you’re training him. Probably not the things you want to train him for, but training him none the less.
Choose wisely. You don’t have to be riding or have him be of ridable age to train him. If you lead him even once, you either do it how you’d like it or how he’d like it.