Brilliant leo
@OP
I've been a dom since I was 18, and probably would have been before that except that it may not have been legal and I am, of course, a law abiding citizen. If you're legal you're old enough. If subs don't want to submit to you then it may be more a matter of demeanor or confidence, with age as the kind/easy letdown. You'll eventually find a sub who wants to play, and then from there get more experience, and it will all snowball. It will be fine.
The particular term 'master' though holds special significance for most people in the scene. I think leo nailed it. Call yourself dominant, be dominant, let subs see that, and then down the road if one of them wants to call you her master then it will be a happy day (or an awkward, crappy day, depending how you feel about her. But let's assume happy.)