Developers building in those areas will either have to devote 15 percent of their units to affordable rentals, or they will have to build affordable units within 2 miles of the new building. If they build affordable units within the 2-mile area, they can't go beyond the boundaries of the pilot and the number of units they build must equal 20 percent of the residences in the new complex. Affordable units are required only for buildings with 10 units or more.