How would you like the students you mentor to add value to the relationship?
Every time I teach my craft to somebody new to web development, I learn something new. It gets me excited about coding again, and it's why I love teaching so much. The students with the most questions are usually the most enthusiastic, so ask any and all questions that come to you. If your mentor doesn't know the answer, even better. I like students who make me think!
Edit: Typo
Like any relationship it works best when both sides have strengths that complement each other.
The nature of a mentor relationship is that the mentor has more experience. It doesn't mean they are more skilled in every way.
A specific example: I get questions from my mentors along the lines of "What's the state of X? Is it ready for prime time?" or "In Y, how does one typically do Z?" because they know I am actively involved in the community for X and Y.
The students were much like your property, you could beat them, treat them basically how you liked, even sodomize them if the mood took I'm guessing.... (sorry to be graphic, but I think that's how it likely went down). You did however, have to provide for their basic needs and you couldn't kill or severely maim them, or it was bad for business. After X number of years, the student could go out on their own, and the process repeated.
So this system has some obvious flaws and has slowly been done away with. It might be good if it were to make a comeback in a modern form (without the beating and sodomy of course). Then again, maybe it's not so good. Still, we get lots of people wanting "mentors". What do they have to give back, particularly at first?
My opinion? Want a good mentor? Look in the mirror.
You know, I don't think so. Trades have been around for a lot longer than universal justice. Slavery is only recently going away. Important people in the community have traditionally done what they wanted and as long as it wasn't too egregious, they usually got away with it.
A little light googling turns up no shortage of cases of apprentice abuse, (including sexual) from the relatively recent past (1600's on... a time that is comparatively modern in the "objective" dispersal of justice). One can only imagine what earlier times were like. No doubt there have been plenty of beneficent individuals, but the beneficent treatment of fellow humans is sadly often the exception historically speaking. For most of human history there has been a very different standard of what was acceptable than we hold today. A third party flogging for failing to follow orders (or simply because the flogger was having a bad day) likely scarcely raised eyebrows as long as it didn't get out of hand for most of human history.
Even today we still see remnants of this relationship. Abuse of underlings who put up with it because they think it will get them somewhere. Taking on an "apprentice" out of sexual interest rather than simple interest in their development. Human nature has not changed terribly much... just the rules.
I don't know what kind of relationship OP is after or what he is willing to do to get it. I do wish him the best of luck on his quest.
Define "going away."