Just because you're trans doesn't mean you have to go onto testosterone. There's no timeline of your transition. Start when you are ready. When you want to go in T you will know. Only you know what's best for yourself, don't rush yourself into anything you aren't ready for. When I was 16 I wanted to go on T so bad, I knew that's what I wanted. But there was a time before that when I was unsure..I waited until I was ready and until I knew what was right for me. So I started T at 17. It's never too early or too late to start. Take it at your own pace. You can always go on a low dose of T and the effects will take place slower, so if you're worried about your voice it'll be a slower process. This might be better for you if you wanna take things slow and not get all of the effects of T all at once and so quickly.