Are there any grants to start a gym?
I would contact the Small Business Administration in your area. And search things like “California Small Business Assitance”, “Small Business support”, “Small Business Programs”, etc. There are a few gyms here now that got investors to help them start up.
I have start and restarted my business several times. I always got a back up job to help with the costs until things got going, if I hadn’t saved up enough money before the restart (which was usually a relocation and restart) to give it a go without the back up job.