As mental health care shifted from state psychiatric hospitals to the community in France and western countries, the mental health system became inevitably involved in housing as it strove to meet the broader psychosocial needs of consumers. Simultaneously, as many consumers found themselves unable to find stable living in the community and struggling with addictions, they became a significant subgroup within a larger homeless population, which has received increasing policy attention over the past three decades. There are two distinct service models for adults who have severe mental illness and are homeless: the residential continuum model and the Housing First model.

Inclusion Criteria:

aged over 18;

• who are absolutely homeless or precariously housed. Absolutely homeless is defined as having had no fixed place to stay for at least the past seven nights with little likelihood of finding a place in the coming month. Precariously housed is defined as being housed a in single room occupancy, rooming house, or hotel/motel as a primary residence AND in the past year having experienced two or more episodes of being absolutely homeless OR one episode of being absolutely homeless that lasted for more than four weeks in the preceding 12 months.
• living with schizophrenia or bipolar disorder (diagnosis of DSM-IV);
• with a sufficient understanding of written and spoken French to be able to provide informed consent and to participate to face-to-face interviews;
• affiliated to a social protection;
• who have lived in the city targeted for at least 6 months and willing to stand in the city during the 2 next years;
• with a global score measured on Multnomah Community Ability Scale (MCAS) (scale <=62 (high need criteria));
• hospitalized at least twice on the past 12 months OR held in prison on the past 24 months OR presenting substance or alcohol abuse or dependence (high need criteria).

Exclusion Criteria:

• being considered unable to provide informed consent;
• having dependent children;
• pregnancy;
• or a DSM-IV Axis I diagnosis other than schizophrenia or bipolar disorder