Franchising can be lucrative, but it can also be pretty scary. Understanding every word of the contract is key. Typically the franchisor holds all the power, has all the rights and all the control over everything. You're not going to be making marketing decisions on your own in most cases. You pay into a marketing fund, and have no control where the $$ gets spent. You likely won't have control over pricing, wages you pay, suppliers, anything. Be VERY CAREFUL what you get yourself into and make sure you have 2 or 3 expert franchise lawyers go over any agreement and pick it apart to the tiniest degree before you think about signing. I've heard of a lot of people getting screwed over by their franchisor.
One guy I know of in particular got screwed big time by Subway. He opened a franchise with them and was doing alright. Then two years in, Subway comes to him and says they are going to open another shop within a short walk of his place. Obviously he doesn't want to see that happen. So they tell him he's got first crack at buying the new shop (in addition to the one he's already invested in). He couldn't afford to do that, and really didn't expect he would gain a whole lot by doing so. Subway went ahead and opened the new place anyways, and the guy lost half his business - to his own chain - and couldn't do a thing about it.