I put my Pilates instructor in business. Equipment for the studio was top-notch and about $15k. Rent is modest as it is a studio. Most of her clients were older people with a fairly high income who benefited from the modest demands Pilates puts on elderly bodies.
She was busy 40 hours a week and charged $50-$70 an hour.
The business doesn't scale unless you have a bigger facility and are great at recruiting new teachers-something she didn't want to do since very few are as good as her. The difference was her personality.
We decided that I wouldn't see the client list, but it became clear to me that she was attracting some of the wealthiest people in town.
Low fixed costs=limited but well-off clientele=client centered personality=success.