Bro that is why your probably only 5'8!! J/K you know I'm fuckin around wit you
I think you can start at a pretty young age, as long as you do it right. It probably isnt smart for a pre-teen to start dedicating his life around weight training, but man has worked out in some sense since the begining of time, and back in the day kids as young as they could walk would go work on the farm/ranch and that is some serious liftin! so I think the bigger question is, what is the right age to start using sups?? and I think that is something you have to take serious!!! I have heard it is pretty solid here that you should wait till your 25 till you start AAS, around 18-21 before you should start pro-hormones, and the really simple things, like multi vits, amino acids, creatine, and other stuff like that, you would probably just gauge it down a little, maybe. But you should also work out for awhile 6-12 months totally natural, learn your body, and what works for it, and go from there...
good luck
Peace