1 - You can pay for the points with cash, credit card or finance through Disney or by your own means (home equity.)
2 - Resorts = Old Key West, Boardwalk, Beach Club Villas (selling now through Disney) , Wilderness Lodge, Vero Beach & Hilton Head.
3 - Through Disney directly 250 points at $80 per point (until end of Nov) = $20,000, after Dec 1, $84 per point = $21,000. You could always try a resale. Don't forget to add in the yearly maintenance costs for your points.
The time of year only matters on how many points are required to get a room, the cost is the same.
I would highly recommend DVC resale. We are just about to close on 350 points at BWV through Jaki at atimeshare.com. We purchased at a significant discount. I figure that our 350 points at resale price would have only bought us 270 points through Disney. (A 2 bdr vs. 1 bdr. during peak season). Good luck!