This forum has done a great job providing a lot of useful information. There have been many similar questions posted in the past where gym owners have provided some great insight as to where to look when starting a gym business.
Although I don’t own a gym here are a few things one might want to consider before opening one (in a simplistic way):
-Location and space (this will determine the rent)
-Business plan (might need to be evaluated every few years)
-Technology involved/offered at the gym
-Type of trainers hired (employees vs. independent contractors)
All of the above can also be influenced by the state and local regulations and laws that are in place. So need to keep that in mind when looking to open and operate a business. This would fall under the legal and accounting factor.
I hope this helps.