In addition to the permitted uses in the underlying B-2 Zone District, when affordable housing is provided, mixed-use buildings shall be permitted with first-floor commercial uses and second- and third-floor residential uses, resulting in structures with a maximum height of three stories and with a residential density up to, but not exceeding, 12 dwelling units per acre. There shall be a mandatory setaside of affordable units. The setaside for rental developments shall be 15%. The setaside for for-sale developments shall be 20%. At least 13% of affordable units shall be affordable to very-low-income households with half of the very-low-income units available to families.