If you did an internship at a gym, you could look for alternate ways for your clients to get assistance paying the gym fees. Does the gym have babysitting while people are working out? Are any of your clients good prospects for doing that job in order to pay their gym fees? I was also wondering if you could barter childcare for training, but that doesn't address the legal aspects.

If your church is willing to assist you in your program, they might also be willing to help pay gym fees for worthy clients?

The only issue I see that might be problematical is if people sign up for the program only to drop out quickly (as so many people often do) leaving them saddled with gym fees they can't afford to pay, or a church obligated for such fees. So I'm not sure this is a perfect solution but it seems to me that if you give it some thought you might be able to figure out how to put together a program that works within the bounds of legal responsibility.