In my mid teens I started taking training seriously and eventually found a gym with many bodybuilders, a dozen of them had been in the bodybuilding magazines. I went along well with them and through reasoning they convinced me not to take steroids, and if I ever did, do it later and do it in a scientific manner, research the compounds, understand how they damage your health, monitor and mitigate those issues. Back then this was nearly impossible, blood work had to be ordered by a doctor or done in another country. Also I realized the costs would mean I would have to work and get by just enough.
Fast forward after 15 years of training I found I had low testosterone which meant everything took a different path.
The difference between me having done steroids then vs as I did, starting in my 30s is as follows;
1) Financial/career. Blood work, a proper diet, all required supplements are nothing for me now, while they'd overwhelm me back then when I was saving money and not making much. I also included the word career because when that it settled (I run my own business), it is several times easier to get on track for a long term plan. Spending a few thousand $ on doing things correctly through proper diet, supplementation, blood work, medicines if needed, may be nothing for me now, but if I spent it back then, I would have lost out on the compound effects of investing that money to be able to make more in the future.
2) Knowledge on hormones, health et.c. I have had years to accumulate knowledge, not to mention the availability of information then vs now is night and day. On one hand this means younger people can make more informed decisions, however I question whether they can digest all the information and make wise choices. I knew I would be on exogenous test for life before starting and acted accordingly. Knowing how to monitor health parameters and adjust AAS usage, diet, supplements, medicines takes some time, especially since there is no one size fits all approach.
3) Training/experience. Even before AAS I had a history of getting injured due to training too hard. Yet still I got myself into big setbacks with the aggression and strength I got from trenbolone, cost me a few thousand $ in PRP/hyaluronic acid treatments in areas with stubborn scar tissue and over 2 years in limbo, no gains. With my love for heavy and hard training, I would have wrecked myself if I used these things earlier.
I guess being extremely gifted and having chances of getting on the Olympia stage can be reasons to start AAS early, but in that case you will have coaches who want to help you due to the sheer talent you possess, and the process will be many times easier vs my path.
If not, I can't see how me in my late teens or early 20s would manage all these things when I didn't have stability and wealth that I had when I was 28 when I started. Even if I did, I would have missed other opportunities because of not focusing on attaining wealth, investing and working my ass off. Just the few thousand $ per year needed, at ages 17-25, would set me back from being able to do other things with that money and the compound effects of using that money properly. I question whether I would have done things right or just ran cycles and assumed all is good as long as I took some time off between the cycles...