At the time of site plan approval for a development in accordance with the Business Development Overlay Zone, the entire tract of land on which the proposed development is to take place shall either be under single ownership or under contracts of purchase to provide single ownership. However, after site plan approval has been granted, subdivision of the entire tract or parcel may be made into individual tracts, provided there is in place a developers agreement approved by the Planning Board. At a minimum, said developer's agreement shall not increase the number of curb cuts and shall control and regulate future land uses, utility access, parking easements and responsibility for maintenance of buildings and site amenities.