In many countries struggling with a shortage of affordable housing, one available instrument is to increase the housing stock at the disposal of local authorities using commercial, residential projects. This solution is called the Inclusionary Housing (IH) model, which creates a mix of residents with different rights to housing and who belong to various social groups. The developer should “pay in apartments” when a residential project benefits primarily from planning and spatial privileges given by the public actor. This instrument has advantages and disadvantages, and its success depends on local social, cultural, and economic conditions. The authors decided to investigate the possible effects of introducing the IH model in Poland considering the results of the application of the Act of July 5, 2018, on facilitating the preparation and implementation of housing investments and accompanying investments (Lex Developer Act). The authors aim to determine the number of apartments that developers could potentially offer to public actors in cities where privileged decisons were applied most often. The research was conducted using methods such as a critical literature review, research of legal acts, analysis of local source data, case studies, and a comparative analysis. The results allow conclusions regarding local housing needs.