This excerpt is from the glossary section of the FetLife website.

Mentor: A trusted adviser or counselor to someone who has already gained basic knowledge and experience. A mentor is a person who has considerable knowledge and experience and usually, in the eyes of the mentee, substantial wisdom. It is widely agreed that a mentor should be on the “same side of the slash” (Dom/Dom or sub/sub). Most people also feel that a mentor does not approach people with offers to mentor them. A mentor does not train, teach or play with the person they are mentoring. A mentor provides advice and suggestions and, for the most part, encourages and recommends resources for their mentee to use in a process of self-learning. This title/role is subject to much abuse on FetLife, by (mostly) dominant males who approach (mostly) female submissives with offers to mentor them as a way of seeking a D/s relationship, or simply sex, with them. Many of those who work to assist new people with safe entry into BDSM warn newbies against all who offer to mentor them because of the prevalence of ulterior motives among those who make such offers