I used www.tagrel.com
On home page, upper left corner, under (DVC) you will find a points calculator. Just put in your dates and it will tell you how many points you will need.
There is a DVC Point Chart link at the upper right of each of the DVC Forums here on the DIS.
You can't actually rent any points since they would be worthless to you unless you are a DVC member. What you would be renting is a reservation made by a member using their points. While you can certainly get an idea about how many points might be needed for a reservation it might be more important to know what the same reservation would cost thru Disney directly so you can compare the value of a member rental.