Although the title asks about Franchises in particular, the first question one must ask is "Am I determined enough to own my own business - of any sort?"
Being a business owner requires the drive to get up in the morning and to do what needs to be done. If you like the idea of being able to get paid even when you are not personally contributing, then perhaps you are better off working for someone else.
But if you are the entrepreneurial type, it boils down to one question: Are you willing to pay (both upfront and on an ongoing basis) for a proven game plan for a business,? Or would you rather roll the dice on the risks of doing it "your way"?
Doing it "your way" lets you reap all the rewards... but, since you are building and implementing a new untried business plan, the risk of failure is much higher.