I didn’t read all the comments so maybe this has been said, but I think one should look at everyone as a mentor. They are either teaching you what works, or they are teaching you what NOT to do.
Viewing everyone as a mentor means that one or a few will resonate deeper with you and you’ll interact and learn more with them more than the rest.
As for identifying intentions or suitability:
1. No abuse of power, labor, sex, or money. Money - you should cover costs. And a small payment for their time is not ridiculous.
Labor - In lieu of cash, small chores (and definitely cleanup from related magical practices) are reasonable.
2. Examine their life - if they are happy, healthy, successful? Those are signs that they’re doing something right. Alternatively, are they sickly, irritable, destitute? Those are signs that you want no part of whatever magic they’re practicing.
3. Lastly, the “right” mentor isn’t going to sell you on or campaign for being your mentor. You should ask them, not the other way around.
Last lastly, there are no superiors on this path. No one is better, we are all on a path of experiences and some who have already been where you are may be happy to share that with you and vice versa.
My “mentor” hates when I refer to him as such, which makes me do it all the more lol, but he swears that he’s learned more from me than I have from him. We are brothers walking the same path and sharing our insights for mutual growth. That is all.