The UK based start-up, "Trusted Housesitters," offers a simple business model for its members. For one annual fee, members can stay at other people's homes for free, as long as they take care of the homeowners' pets. "Trusted Housesitters" expanded into the United States this spring. Andy Peck, Founder & CEO of the company, says the service is now available to members in 150 countries, and is doubling membership year over year.