We applied grounded theory methodology to generate a working relationship model that influences motivation for stable housing among homeless people with serious mental illness, to understand the role of a working relationship in critical service transitions. We focused on practitioners' perspectives and practices in Critical Time Intervention (CTI), a community intervention aimed to reduce homelessness through providing support during the transition from institutional to community living. We found a working relationship that highlighted "nonauthoritative" and "humanistic" features. Workers respected client autonomy and maintained flexibility in the format of client contact and service activities. They used practice strategies including following client leads and informal relating approaches to facilitate the development of client trust. The trusting relationship enhanced client interest in obtaining housing and the commitment to the transformation crucial for retaining housing. We discuss the significance of the relationship and ethical considerations of relationship-building activities in community mental health practices.