I assume you are purchasing a resale and not through Disney (if purchasing through Disney you do not have to wait for closing but can start reserving as soon as you return signed contracts and are approved). With a resale, it usually takes up to a week after the closing for you to be placed in Disney's system so you can make reservations. Thus, you are talking about trying to get early December time less than 3 weeks out. Chances are slim because (a) it is often difficult to get anything that close to a date most times of year, and (b) December (entire month) happens to be the highest DVC demand time of the year (it is hard to get anything even 7 months out). Note that doesn't mean you should not try, weekends (Fri and Sat night) tend to be available later than weekday nights (Sun to Thurs) and cancellations can occur opening something up.
Awesome. Thank you. I will try my luck, if not, I will just book a cash ressie at a value or mod. I am looking to take my sister down for a mini weekend trip. I haven't seen her since she left for college and I think it would be nice to spend some time just the two of us together.