Do they sign up or are the contacted?

I'm not sure if families sign up, but I do know for sure they contact families. My aunt and uncle live an alternative lifestyle (very earth friendly) and the producers contacted them after seeing a newspaper article about them.

They contacted my friends as well - they own their own business and home school and had never watched the show. They declined but we have all had a hell of a time laughing about what they could have done on camera if they had done it :-)