There is a rather common weed here, called lamb's quarters, that is a delicacy in salads in five-star restaurants. And to think I have a gourmet treat growing wild in my garden! and my yard! and my pasture!
Passion fruit, which my grandma called maypops, also grow wild here. (Tennessee)
http://bioengr.ag.utk.edu/extension/extpubs/PlanList97.htm
Has plans for many agricultural type buildings.
See especially http://bioengr.ag.utk.edu/extension/extpubs/Plans/6356.pdf
This is a "pavilion" with storage that might suit your needs.