The "Revitalizing Downtowns and Main Streets Act" introduces a new investment tax credit to encourage the conversion of non-residential buildings into affordable housing. This credit, known as the Affordable Housing Conversion Credit, provides an amount equal to 20 percent of a taxpayer's qualified conversion expenditures. It applies to buildings placed in service during the taxable year, aiming to address housing shortages and revitalize communities.

Qualified conversion expenditures are capital account charges for depreciable property, incurred during a two-year conversion period, and exclude acquisition costs, though brownfield cleanup is included. A qualified conversion requires expenditures to exceed the greater of 50 percent of the building's adjusted basis or $100,000. The original building must be at least 20 years old and nonresidential real property immediately prior to conversion. A qualified affordable housing building must reserve at least 20 percent of its residential units as rent-restricted for individuals earning 80 percent or less of the area median income for a 30-year period.

The credit amount is limited by allocations from State housing credit agencies, which operate under a national qualified conversion credit limitation of $12 billion. An additional $3 billion is available for buildings located in economically distressed areas. Agencies must develop allocation plans with selection criteria, including financial feasibility, the extent of affordable housing creation, proximity to transportation and employment, support for small businesses, and local government support.

Special rules increase the credit to 30 percent for buildings in qualified census tracts or difficult development areas if 20 percent of units are for individuals at 60 percent or less of area median income. Furthermore, a 35 percent credit is available for historic preservation projects in rural areas, capped at $2 million of expenditures. The credit is also made transferable, allowing taxpayers to sell the credit to other entities. These amendments apply to qualified affordable housing buildings placed in service after the bill's enactment.