If you own 170 VWL and add-on 50 at another resort, you have the 11 month window at VWL for the 170 only and at the other resort for the 50 only. You don't get to mix the two together to claim 11 month ressie rights at both for the full 220. Minimum add-on is 25 points if paying cash, 50 if using financing, and 100 (at WDW resorts) for use of Magical Beginnings (where you sell back first year points to Disney to satisfy part of down payment --at VB and HH you can use Magical Beginnings at the 50 point add-on level.