The first thing you probably should know about having a mentor is that a mentor is defined as:
Someone who was once where you are now and is now at a place you want to be and is willing to assist you to make the jump.
This means that only someone making moves towards where I am interested in going should be my mentor. A poor man can rarely mentor you into riches, if he knew how to be rich, he would not be poor, would he? A bricklayer cannot mentor you to become a civil engineer, you would have to seek someone else.
The person has to be willing to assist. You have to keep in touch with her, she also has to keep an eye on your progress and monitor you and pump you up to get things done. Do not confuse mentors with role models, for example, unless you figured out a way to talk to the dead, guys like Albert Einstein cannot mentor you. You can read his books and learn from his story, but he is merely a role model to you and nothing more.
Is mentorship compulsory? NO.
It merely makes things easier as you get to leverage on the experiences of your mentor without partaking in the pain it took to learn those lessons.