This paper discusses the prerequisites of inclusive housing development based on the learnings from Ars Longa, a block of flats for artists, designers and authors in Helsinki, Finland, that was initiated by a group of elderly persons. The study draws from research on co-design and universal design in housing. Post Occupancy Evaluation is used as method of investigation. Interviews with four key actors trace the barriers and enabling factors in the housing development process and assess the final design outcome. The results highlight the role of public institutions in supporting resident-driven projects, the financing of projects as major barrier to laypeople, and the potential of concept design in integrating the needs of stakeholders. Joint design with adjacent plots made extensive shared spaces feasible and clever design moves enabled spatial flexibility, whereas the connection of co-design activities to building design was deemed weak. The study shows that continuous management and community building are needed for negotiating the use of spaces and for fostering agency and belonging among residents. The paper contributes to research on inclusive housing development through an empirical case.