Lots of people choose to go into business with those they already know very well, especially close friends & family. You'll hear widely varying stories of success with those relationships though - many are ruined by reliance on such familiar beginnings and then a letdown of expectations when the real work begins. As The Notorious B.I.G. once said (among many others, haha) "Money & blood don't mix." My 2 cents. Personally, I think a work colleague or someone whom you began a relationship with through networking & mutual interest in a market opportunity is your best bet for a partner. Not family or old friends.