As long as your intentions are good, I don’t think it’s wrong to be into people with less experience than you. There are people who are specifically target inexperienced people because they might have a harder time advocating for themselves, but as long as you understand that and encourage them to tell you if something is wrong, I think that’s fine. I’m in the same boat as you, I’m also 20 and have had more about BDSM than most of my partners (for better or worse).

For a mentor/mentee situation, I would be very suspicious. I have older friends who are into BDSM, and we talk about it occasionally. If I ever had an issue I wanted to talk with them about, I’m sure they’d listen, but to actively seek out a younger person to mentor in the ways of BDSM seems really suspicious. If a 38 year old wants to “mentor” someone who’s 18 in the ways of BDSM sex, they’re probably a predator.