I set up a salad bar on my own, that was similar to a franchise chain and refinanced my house for the money needed. It was very hard work and I made no money, despite the place being hugely popular. On the other hand, it was great to get to know all the people in the area and we made some great friendships that last to this day.
If you join a franchise, make sure it is worth the fees. Chains like Subway do excellent research into location, menus, production lines etc. The branding is a huge drawcard, and buying power can mean the ingredients are cheaper. However, smaller franchises can provide very little and hence not be worth the fee.
There was a coffee franchise next to us and the owner eventually dropped the franchise and renamed. He was paying a fee, and got nothing in return, as it was too small to have any branding or buying power benefits.
Check out the franchise you are considering in several other locations and see how they go. Speak to the owners to find out what their experience has been. I have seen great sub restaurants next to Subways that are empty, despite offering great menus and better prices, simply because people are sheep and go to the place that they recognise.
If you have not been in the industry, a franchise can be a good way to start, if it is well run. The owners can show you the best techniques, should know the best places to get ingredients, teach you how to forecast the correct amount to prepare each day. Wages and waste are the two features that will make or break you, so guidance with that is critical. If you choose not to go with a frachise but go out on your own instead, than I strongly recommend you work in the industry as an employee for at least a year to learn exactly what is involved.