Efforts have been made to minimize the cost of affordable housing through modular construction, prefabrication, economies of scale, and low-cost materials. However, there is a gap in the literature regarding the integration of the varying sizes of the units with design optimization to mutually benefit developers and potential residents of affordable homes. This research introduces an optimization model to integrate optimization with ranges of units’ dimensions. The model proposed exploits the variations in the reinforced concrete cost versus area by applying several scenarios. Available options are tailored to optimize the reinforced concrete floor cost of housing units by varying the rooms’ dimensions.