Rent is income, but share expenses are not income, according to my wife, the Enrolled Agent Tax Professional. She recommends a set level of contribution to household expenses, rather than having one person pay the taxes, another pay the insurance, and others the other expenses. Thus, all of the money goes into a single, shared pot to cover all expenses. That requires a detailed budget and careful disbursing from the shared pot. This arrangement will pass muster with the IRS as shared expenses and not rent. Thus, it will not be income for any of the residents.