In my opinion, this is one of the negatives for buying through resale. It takes a while for a resale to pass disney's right of first refusal. Then the contract has to be transferred and sent to disney and then wait for disney to put it into the computer system before your points are put into your name. That can take months from the time you "bought" your resale.
If you are very flexible you can find a place for may, but it may not be your home resort or your first choice of accomodations.
The pro to resales is definately savings.
The con to resales is waiting for your contract to go through and get posted to the system.
If you buy dvc through disney for new or sold out resorts, you can make your reservations within the week you buy from them, prior to signing the contracts. If you don't go through with the purchase they will simply cancel your reservation.