The Legal Moves podcast discusses considerations for design partnerships:
http://www.strebecklaw.com/legal-moves-episode-2-partner-up-or-go-solo-part-1-with-jeremy-commandeur-and-brian-henk/
http://www.strebecklaw.com/legal-moves-episode-03-partner-up-or-go-solo-part-2-with-jeremy-commandeur-and-brian-henk/