Hi Hebe!
I don't quite understand what you need, maybe more context would be helpful to understand what you're looking for... I thought of a cooperative, but I'm not sure.
Hope these links help you
http://en.wikipedia.org/wiki/Corporations_law
http://en.wikipedia.org/wiki/Cooperative
http://www.myownbusiness.org/espanol/s4/index.html#2 (there's also the english version)
Good luck!