You don't actually "rent points". What you do is pay a member to use their points to make a reservation in your name. For a rough idea as to cost, take a look at
http://***********/Points/2006/vwl.shtml to see how many points you will need (it only goes through 2007 but points per night should be about the same in 2008 - just adjust the dates for holidays). What you will pay per point depends upon what you can negotiate from a member. Market price has been stuck at close to $10/point for a while now. Some people pay more, some pay less. But I'd figure $12/point for your budgeting. Keep in mind that there is no tax on this transaction, so a rental at $333/night is about about the same as getting a hotel for $299/night.
The good news is, you can get a very nice room this way for less than Disney would charge. But keep in mind the drawbacks.
1. This is a private transaction that invovles your sending lots of money to a private citizen, and them being responsible if you damage
DVC's property. Trust is needed on both sides.
2. You need to plan far ahead, as some of the resorts are small and getting a reservation can be tricky. Ideally you want to be making a reservation at least 7 months ahead of time; 11 months is even better.
3. Going through DVC, you don't get full maid service for your room.
Hmmm. The DIS doesn't like that link. How about this one
http://www.wdwinfo.com/disney-vacation-club/DVCpoints.shtml