Lot's of great questions.

You say you live in a small/med sized town and there are already 2 chain gyms and a smaller gym with no classes. I assume the chain gyms offer classes. In which case I would think you might have too much competition. Aside from the no-contract classes, what else would set you apart? What would make folks frequent your place rather than the others? Can you find teachers for your classes in your area?

When you write your business plan you will need to answer all of your own questions so you need to expand your research. For example, rather than asking us here how much it would cost to do a build out, you need to contact contractors to get a very good estimation of costs.

You will find that your start up and ongoing costs will be considerable. In addition to the build out you need to factor in liability insurance, utilities, advertising, payroll, permits, decorating, office machines, furniture, taxes, etc., etc., etc.

I will also assume that you will require a loan. The fact that you have no experience in the industry will be a huge hurdle. You will not be able to secure an SBA guaranteed loan without experience. You would also need to contribute about 20 - 30% of the start up costs yourself (cash).

If after you complete your business plan's financial statements, you find the costs to be too prohibitive you might consider going about this plan differently. Maybe instead of trying to bring in another full sized, full service gym, you could scale it down to just the classes you know the other gyms don't offer. Pilates and yoga are all the rage and I would guess the other gyms already off those classes. If not, then there is your niche.

Good luck to you!