Kosts are popular urban room rental facilities in Indonesia in which tenants from various backgrounds live together and share the common space. As the majority do not comply with the regulations, many are unregistered, overcrowded, and have low living condition. This study analyzes kosts' social environment and issues based on tenants' experience through questionnaire and interviews. Tenants tend to be tolerant, adaptable, and positive toward kosts' living environment, but lack of sense of belonging to their neighborhood. Tenant-neighborhood interactions and mutual views tend not to exist. Public education, strict regulations, effective neighborhood information system, and domain for regular interactions are necessary for improvement.