Have you thought about opening your own independent sub shop? There are, of course, many benefits with franchising (name, support, etc.), but there are also drawbacks over and above the fees. You likely lose potential customers that had a bad experience at other franchise stores, or just don't like the product in general. I don't like Subway, for example, and don't go to any store.
We had a local sub shop where I live for a long time. It was a mom and pop operation in an OK (not great) location and stayed open for years, then was sold and quickly went out of business. Their product was light years ahead of any chain out there. They used better ingredients and could change their menu in a pinch if they kept getting requests for something different.
Yes, its much less turnkey to go independent, but there are restaurant consultants all over the place that can be helpful. A coupon ad campaign to local businesses and area homes could be your marketing plan -- few go out of their way for sub sandwiches. Like anything else, location is your most important asset and you can be forced into a place that isn't the best if you go with a franchise.
I would not jump into this thing without 6-8 months of solid marketing research about ANY sub shop in your area. There's a Jersey Mikes in a location where a Lenny's failed near me. The Lenny's changed their business hours (closing early), then closed for good. Who knows if it was improperly managed, didn't have sufficient capital, or what the issue was. However, I wouldn't feel real good about going into the same spot where another business that's the same as I am in previously failed. At least, I would want to know what happened. So you need to go to the local stores and see who was in the place you're going into and what issues, if any, they had.
I think I've eaten at JM a time or two. In my opinion, what is really needed is something different than the Lenny's, Jimmie Johns, Subway, and even Jersey Mike's. Not that these are bad places, but when the chain makes a change and forces all franchisees to change, you piss off customers (I won't go to JJ for that reason). I'd kill for a local mom and pop sub shop that used fresh, locally baked bread, good ingredients, and would make a sandwich like the customer wants instead of like the chain wants.
One more thing: if you aren't planning on being there most of the time, don't bother. A small restaurant franchise isn't an investment; its a job. Now you may make a lot of money at that job, and you may later have the ability to expand locations and back off a little from the day to day running of the store after its established, but to start, plan on 80+ hour weeks.
Sorry for the length. Take or leave any of this, but I've counseled small business and litigated conflicts for a long time.