When the planning commission has approved a project master plan for development, no subsequent phase shall be considered until the prior phase is fifty one percent (51%) sold and recorded in either a trust or warranty deed, or a quitclaim deed, with the county recorder, or the developer may furnish certified copies of real estate purchase contracts to be reviewed and approved by the county attorney; additionally, all improvements in the current phase shall be completed. (1998 Code § 16.12.070)