Renting points to take a cruise is not really a way to save money on the cruise. Usually, it is normally recommended on the boards here that even owners not use their points for cruising, but rent them out and use the proceeds to pay for their cruise. Of course, some people do use their points directly for cruising.
I think there are no more 2011 cruises (at least on one ship) that can be booked on points at this time - they have already allocated and sold all the rooms that could be booked on points.