Why not just rent points?

[dreamprfct]

My question probably shows my ignorance so here goes:
Last week we almost bought into DVC--last day of cruise etc--however we were the last meeting of the night and the computers went down--so we didnt get to and basically rethought everything over night and thought we should research some more--
which brings me to all of you!

We were looking at Aulani-
here are my questions:
1) why not just rent points (without buying) whenever I need them?
2) what are the restrictions with buying resale if we choose to?

thanks!!