Here is something you usually find near Colleges, Pita Pit.
I have enjoyed their fine food skiing in Whistler BC at 3:00 AM, driving 120+ miles to Western Washington University at 2:00 AM from Seattle, and stopping by the local one down here in San Jose, CA. Pretty good cheap food, and when you are craving it.. you're craving it.
Pita Pit food is quick to prepare, conveyor line operation, and cheap. I knew a lot of friends at WWU who would eat there three to four times a week.
Pita Pit Canada Web Site
Pita Pit USA Web Site
Unluck Subway, Quizno's, etc, you do not see them on every corner. There only two in the Bay Area, thirteen in Washington State (my two 'stomping' grounds).
Not sure about ROI, but I imagine it is online with Subway. The only negative I can think of is that the Pita's MUST be ordered from Canada, and the Pita Pit in San Jose sometimes runs out...