In most countries I know of, you don't need a teaching qualification to set up a language school. Some countries may have this requirement but as you don't say where you intend to work, I can't advise. While a teaching qualification is not essential, it would certainly help you in dealing with day-to-day issues: hiring teachers, teachers who seek advice; students complaining....
Useful qualifications would be: accountancy, marketing, human resource legislation of the country you wish to work in. You could take a look here for tips on school management:ESL School Administration