The primary source of revenue for gym businesses are membership fees. Typically, members pay month-to-month, or fulfill a year-long contract. Members are also usually able to pay for a full year upfront for a discount.
The key expenses for a gym business are the costs associated with payroll, purchase and maintenance of gym equipment, cleaning supplies, marketing costs, and working capital. Other expenses will be rent, utilities, taxes, accounts payable, and other licensing fees (if necessary).