It depends on whether or not it’s considered “prime time” or “down time”, it also depends on how many hours per week they wish to rent the space. I required a 2 hour per week minimum for my group exercise/dance class renters to be paid in advance with a security deposit.
For personal trainers it gets a bit tricky. The more hours they would rent the lower the price would be.
I charged $30 per hour for dance classes and $10-15 per hour for trainers.
Your location, parking, and your studio overhead will also make a difference when factoring price.
Remember to treat this like a business, they all need their own liablility insurance etc.