The main purpose of the Supporting Projects to Unleash Residential Housing Act, also known as the SPUR Housing Act, is to encourage the construction of new housing developments by providing financial assistance to developers. This assistance is aimed at offsetting state and local taxes as well as impact fees that developers incur when building new housing. The goal is to alleviate housing shortages and promote the development of affordable housing options. Key provisions of the Act include the establishment of a grant program by the Secretary of Housing and Urban Development.