First cycle ever, a couple questions

Hey everyone thanks for reading. I am going to do a cycle in the near future, but I don't think I want to do any cycles after that. Will I experience any side effects from only doing one cycle, such as losing the muscle gained even if I continue working out, albeit naturally? Also, as an 18 year old male, could one cycle leave me with any adverse long-term effects? Do you think I should wait until I am older, to start using steroids? I have read about people who start too early in life having more dramatically low testosterone levels than average steroid users, but I am not sure if this would apply if I only did one cycle.

Any response is appreciated, and I am sorry for asking questions which are probably very simple to you guys/girls =).

First you should hold off till you have built all u can naturaly . that being said
What are you going to cycle ? For how long?and have you thought about Ai's & PCT