in the US, 16 is very early, and a great time to start, earlier is always better, but there are limitations before 18. Since your parents are supportive, you can get past a lot of that with their help. As long as you start soon you'll be fine, it's mostly around the age of 25 when the growth process stops and male genetics set in. None of the numbers you find are exact, some guys go bald by 21, others stay youthful through their 30s, really it's best to start as soon as you can just in case.