Well I've been selling Lufa I grew here in my back yard.
And Hopefully I'll take my first towers to market this weekend.
We have been working on something similar. We have been talking about a year round CSA and farmers market, that would coordinate crops to cater to what the local customers would prefer. It is not off the ground yet.
Hello Chi Ma,
I would recommend reading chapter 14 of Bill Mollison's, "Permaculture: A Designers' Handbook". It is full of information on City Farms, Farm Clubs, etc. with plenty of diagrams of cost structures and such.