A tract of ground, or contiguous group of tracts - whether or not separated by a public street, railroad, stream, or similar intervening feature - for which an applicant seeks approval as an Age-Restricted Residential Development pursuant to this section, shall contain a minimum of 150 acres. Once approved as an Age-Restricted Residential Development, the development must proceed as an integrated entity that must remain in perpetuity as a unified development subject to Restrictive Covenants and no portion of the property shall be sold, conveyed, or otherwise divided in a manner that would create a separate parcel independent from the Age-Restricted Residential Development, unless expressly authorized by subsequent amendment or approval under this section.