We purchased a BWV resale through Jaki Apetz at "A Timeshare Broker". Here's that link...
http://www.atimeshare.com/disney/
Jaki was wonderful, and the entire process took us about a month...which is really quick. Once you and a seller have agreed on a price, the contract goes before Disney and they have the right to purchase the points at the same price you offered. This is called their First Right of Refusal. That process usually takes 3-4 weeks (in our case, it was only two weeks to clear ROFR).
Then you close, and it's a done deal.
I would also check the timeshare broker at the top of this forum...
http://www.wdwinfo.com/timeshare/dvclisting.cfm as well as Shontell Crawford at Timeshares By Resale
http://www.dvcbyresale.com/Contact us.html
Adding on points is something you can only really do through Disney...and you will retain the original membership number, as well as use year.
When figuring resale cost per point, remember:
1. Buyers often have to pay the $400-500 closing cost. On a 100 point contract, that's up to $5 per point. No closing costs through Disney.
2. Resale contracts can be "stripped down", meaning that some or all of the current year's points may already have been used. Also, they might have borrowed and used next year's points as well. All of these should affect the price per point you are willing to pay.
Either purchase method (direct through Disney or resale) is a good way to acquire vacation points. We've done both. The main thing is to figure out which
DVC resort you want to stay at the most, and if it's OKW, BWV, or VWL then you really have to go to the resale market since Disney doesn't sell those anymore. BCV is sold out but some have reported luck in getting new contracts through Disney on that. For SSR, buying direct from Disney is your only option at this time...and don't forget that SSR has a longer Right to Use period of 50 years vs. the 38 years of the other DVC contracts.
Good luck in your hunt!