Honestly you don't need a business degree to open a personal training business. The most important qualification is that you are certified to be a personal trainer, and obtain the proper documents to open a location. If you plan on handling the books and stuff like that, accounting courses definitely can't hurt. If you plan on developing franchises, then marketing and other business courses will help. What you are doing is selling a service. The key thing here is the ability to sell yourself and your business. People would be investing their hard earned money. One question you may ask yourself is, why should they go to you instead of an already established gym or a widely known trainer? I hope this helps.