Start with a strong, honest self-examination of your strengths and weaknesses.
Have you previously worked in an all-commission-based compensation system before?
Are you a strong self-starter? Do you have an inquisitive, sometimes skeptical mind? Are you analytical? Do you network easily? Are you highly competitive or more collaborative? Fancy yourself to be a star or member of a bigger team?
Interview/Network with a number of agents/brokers...try to find people with your background, whether that be straight out of school, mid-life career-change, or retirement career...figure out what's worked and what hasn't for these people, and how it might apply to you.
Once you answer these, your questions on commission split, mentoring, training, monthly fees, etc. should be more apparent. Don't forget--this is a business you pay to go to work in.
All that said, you will come down to a set of priorities--needs and wants that you need to find or match in not just the broker, but also the office culture...even within the same company name (brand), you're going to find differences with brokers, office cultures, etc. One of them will be right for you, hopefully in an area you're interested (i.e. close to home or serving the area you want to work).