Starting your own club from fresh is exciting! You don't have to worry so much about integrating your ideas with the gym's current ways, because it's fresh! On the other hand, buying an existing gymnastics club could mean already having a good number of students and gymnasts already enrolled, and not having to worry so much of advertising it and getting people to come join. Then again, you know, 'build it and they will come'! Especially if you're a well known respected coach, they will come.