Mainstream programs that provide care and services to low-income people consistently assess and respond to their housing needs. Ensuring that public institutions (hospitals, prisons, jails, mental health facilities) are discharging people into housing is equally important.

Most people who become homeless are eligible for assistance from mainstream systems of care, and many are or recently have been active clients of one or more of these systems. Studies on where homeless people have lived immediately before becoming homeless show trends that suggest solutions. Public systems or institutions, such as jails and prisons, hospitals, the child welfare system and mental health facilities, too often "graduate" people directly into the homeless system. One aspect of prevention is to stop these discharges into homelessness, through basic transition planning so that people leaving these institutions have stable housing and some means for maintaining it.

Other people who become homeless still are, or should be, clients of mainstream systems of care. These systems can prevent homelessness by paying attention to the housing stability of the people they assist, particularly those who are at greatest risk of homelessness due to lack of family supports, extremely low incomes, mental illness or other personal difficulties.