Revenue Share between Clubs and Personal Trainers

I am trying to figure out a fair compensation system for the personal trainers that work in our club. We are located in Red Deer AB, Canada. Right now we have a contractor trainer. We pay the trainer $15 for each new client's first session which is included in with their membership. Our trainers then charge $40/ session for any sessions thereafter and we don't take anything from them.

I would like to know what kind of pay structure most clubs use when paying a contract personal trainer. Percentages they take perhaps? How many free sessions for the club /month? I don't think we are standard in how are trainers are paid. Please help me or direct me to where I can find what's fair for both the trainers and the club.