Article continues below advertisementBig Brother contestants live under strict guidelines while they compete for a chance at $750,000. While forming alliances and campaigning for survival, they must adhere to a comprehensive set of rules that govern their time in the house.Article continues below advertisementThe popular CBS reality series, which kicks off its 27th season on July 10, has showcased the lives of Houseguests for 25 years. As cameras roll 24/7, here are the essential rules every contestant must follow.Article continues below advertisementSource: CBS Broadcasting, Inc.