Is it even possible to purchase the building? I would guess that since it’s commercial real estate, you’re going to find a purchase of the land and building would be prohibitively expensive because they’re going to value the present value of the lost revenue over many years.
If you’re going to borrow equipment, you might be better of leasing the space.
Not to be pessimistic because half of gyms survive, but gyms have out-paced restaurants in terms of percentage of businesses that go out of business. You would want a really solid business plan before even thinking of something like this.
…and an LLC or C-corporation to purchase and maintain the gym. Put something between you and your personal assets.