I think you could negotiate (if you haven’t already) a %80-%20 split of your revenues (you keep the %80). I believe that is a fair split, since you don’t own the studio and all the fees that come with it. The other option for you is to completely leave the gym and train your clients at their location or home. You get to keep all the money and you will be eliminating all the going back and forth with the gym owner. You might have to invest little money to buy some equipment that you can take to your clients’ homes and then enjoy all the revenue for yourself.