If you are planning on taking payments for memberships and services, you will also need to factor in merchant vendors/payment gateway % and credit card terminal rent.
Also, depending on how you are going to set up your gym (front desk with staffed hours or 24 hour access), you will have to factor in the equipment and service fees.
If you are planning on selling any kind of merchandise, you will also need to look into a POS/Quickbooks accounting system.
Also, if you want to look into gym management software, you will have to find something that benefits your gym operations and then factor in those costs as well.
I wish you well. As Sue said, it is not easy. But being your own boss in the fitness industry is well worth it!