Preliminary approval may be granted on the complete proposed garden apartment and/or townhouse project. However, final approvals shall be stayed. The maximum number of dwelling units granted final approval in the first section shall be limited to 150 dwelling units. Thereafter, application for final approval of additional sections not excluding 100 dwelling units, may be submitted upon filing of proof with the planning board that 75% of the dwelling units in each previous section granted final approval are rented or sold.