I'm actually in the grocery business and know the economics of opening stores - you can open a store for practically nothing: you start as a convenience store selling staples like toilet paper, long shelf life foods, local produce and whatever the owner makes themselves (ethnic food, apple pies, etc). Then, you slowly add SKUs as you grow.

The rich call this a "food desert," urbanites call this the bodega or corner korean market and europeans have zillions of these. I actually love shopping in these places - terrific & patient service and amazing finds if you're patient.

The food distribution business is beautiful that way - economies of scale are very gentle. It's the exact opposite of automobiles and infrastructure software.

p.s. amazon+UPS is another great stopgap for these communities, and surprisingly efficient if they setup a DC (distribution center) somewhere a few hrs away with more limited selection. It's the 2016 equivalent of the milkman.

As a matter of fact, I do live in a small town with a median household income of less than $30,000. There is a Walmart store. Most Walmart employees do not qualify for food stamps, but they do get health and other benefits not available at many local small businesses. There are relatively high paying jobs at the Walmart store -- much higher than are typically available at local small businesses. And, if a Walmart employee is willing to relocate, there is even more advancement potential.

I cannot imagine anywhere in the lower 48 United States where there could be a community in which people have to drive three hours to get food. If there is, the demand would certainly justify someone from inside or outside the community opening a grocery store. A large capital outlay would not be necessary.