This Guide to Financing the Community Supported Farm in Vermont (published by the UVM Center for Sustainable Agriculture) is an excellent resource that explains federal and state securities laws, equity financing, and a variety of other approaches to covering the costs associated with purchasing and operating a community supported farm. The case studies are particularly enlightening.
http://www.uvm.edu/newfarmer/?Page=business/community-supported-farm-guide.html&SM=business/sub-menu.html