when you are a club employee, some clubs take as much as 50% but provide you with insurance and access to members.As an independent trainer at a club, you pay for your own insurance but the club provides you with the equipment to train people. Some clubs will ask for a fee per person, others will want you to pay a flat weekly or monthly fee.
How much you SHOULD pay is a difficult question to answer because independent trainers are not in a very good negotiating position (unless you are such a well-known trainer that clubs are fighting over you). I would try to get to a point where I keep at least 75 % of what my clients pay me as an independent trainer.
Karin’s and Sue’s answers are right on. The question of liability coverage is crucial. The simplest answer is to acknowledge that is the arrangement that you make with the club’s manager is right for you. If you can, check with an attorney to make sure you are covered and that you will have an opportunity to make a reasonable profit for your time.