My first response was pretty curt, I will make some other comments about franchises over my 10 years of experience loaning to them.
They work very well in two instances:
1) Franchised Fast Food - Especially if you have the money to diversify your risk with a couple of locations. The larger the franchise the better, but usually it requires more capital. These tend to be mildly profitable per location, with a few of them hitting some very large numbers. The corporate parent often will struggle with managing labor, food costs, and theft where a local, active owner is much better. The SBA has many default lists available that'll expose the ones that work verses the ones that don't.
2) Limited Service Hotels: These are more of a real estate investment, but require a franchisee's reservation system and credibility. Since the capital required is really high, it tends to be independent owners that franchise these. The big REITs go after the $10-$20mil properties.
The other really good indication of the quality of the franchise is how much do they want up front in licensing, startup ect, verses how much do they want in on-going royalties? The really good franchises I see will make deals with experienced operators for a very low up-front franchise fee and step-up royalties. They would rather get a great operator on board and profit through higher sales and royalties three years from now verses the biggest fee possible up front.
Dunkin Donuts is a classic example: They used to be family owned and just wanted to extract the highest franchise fee possible out of a new location without providing them any support. They were bought out by a PEG and since went public, now they operate completely opposite. Dunkin now cuts deals with professional operators to get them in and will provide them deals on royalties and advertising early on to support their growth.
I hope this helps, good luck with your decisions.