As in many prospering cities with an ongoing population growth the Berlin housing market is also lacking in affordable housing. The structural housing deficit mainly affects disadvantaged population groups with the result that the housing market loses its integrative power. There is an urgent need for action. In order to make the best possible use of the municipal scope for action, taking into consideration socially balanced and urbanly qualified aspects, since 2014 uniform guidelines have been laid down for the conclusion of urban development contracts in the state of Berlin. According to the Berlin model of cooperative building development, project developers are involved in the development costs of the project. This applies particularly to the production costs of social and technical infrastructure. In addition, in order to create affordable living space, a share of rent-controlled and occupancy-controlled flats is contractually assured.