First thing I would consider is do you have to do it through a franchise. What will you get that you won't get if you did it alone.
Is it a big chain with a identity in the market place and some kudos?
Do they support you in a way that you wouldn't get if you did it alone?
Do they help with advertising, referels, website, etc etc.
Basicly what do you get for your money?
Do they already have a number of franchise you can have a look at?
Are there lots of franchises up for resell, do they even make that possible?
I looked at a few small scale franchises and was shocked at how little you got for the money, one was a chocolate fountain company, it was very expensive. Ok you got one fountain, a few logo t-shirts and aprons and a manual plus advertising on their crappy website that never came up on a search engine.
Whereas you could buy a machine from a company direct they included a manual and training. Logo t-shirts aren't going to break the bank and an IT student (or any teenager) could do a basic website, couple of free editorials in the local press and you are on the way for half as much.