We purchased in 1993 and shortly after that my brother, who had previously wanted to buy
DVC, but wouldn't have the time to use the minimum number of points each year, asked us to add on to our contract for him, so we did an 85 point contract add-on in our name, and basically my brother got to use those points (He paid for them). Trusting, wasn't he?
A few years later, when he was ready for more points, we checked with our advisor, and Disney actually did the transfer from our name to his. The only cost was the closing fees associated with the 'sale'. Disney handled everything internally just as if it were their sale. Because we were staying within the family, Disney waived it's right of first refusal.
The only other condition was that my brother also bought additional points so that his total then met Disney's newly established 150 point minimum.
Remember that the 85 point add-on was a separate contract originally, so it could be sold. If you have more than one contract, you could probably sell one of them. But if all your points are on one contract, I don't think you can split it up and sell only part of it.