After reading another article about GRN, it is basically a travel agency that has access to timeshare rentals. If you join, the availability of timeshare condos will be subject to the same restraints that TS owners have to RCI Extra Vacation Rentals and Last Call rentals. You can go to
Condo Direct, and rent the same thing without paying $3000 to join.
There are lots of other TS rental sites that do not require that you pay $3000 upfront to rent.