One largely overlooked factor in most neighborhoods are all those front yards that get plenty of sunlight and could be turned into another garden space.
If you aren't very good about spraying weed killer on your lawn (like me) then you will find out very quickly that Mother Nature will fill your yard with wild edibles.

Chickweed & dandelions account for about a 1/3 of my front lawn. I've noticed in the city here the poor neighborhoods yards are almost all full of those two as well as wild onions, wood sorrel, etc.