I started at 20 so far I'm ok man, got some small gyno but think that was from when I was a kid, I was super fat till i was 18. My advice to you is train as long as you can without the juice and read as much as possible. If you take steroids or drugs you really need to know what you are doing and get a good doctor, seriously look for a goooood doctor. Take small amounts don't listend to the juice heads that will tell you that you need 2-3 mill per week of sus 250 and 300mg of deca, they just want to make $ off you. remember the quicker the gain the more the side effects
edit im 28 no dude