Do you need a “starter” gym because you feel like you don’t have enough experience to get a job at a larger gym?
One of the things you can do is look for small studios/gyms that are not part of a chain where you are most likely to find your target client.
Another route you can go is getting a related job in a gym while you build up your practical expertise. For example, right now I am certified as a personal trainer but not as a group fitness instructor. I’ve been certified for 3 years and had a tough time trying to find a job as a trainer for one reason or another and someone tried to tell me about starter gyms. In any case, I just got a job teaching group fitness at a brand new club in town. If I ever want to add personal training, then they know me already. It’s kind of a back door way into personal training.
Also, be sure to look at taking on a few clients independently, away from the gym.