Congratulations and welcome home! And welcome to the DIS
DVC Forums, too.
Yes, it is actually a common occurence to have cash availability and not DVC availability. Sometimes there will be DVC availability, but not cash availability.
The inventory of rooms available to DVC are separate from those available for cash. The cash availability comes from several sources:
1. The largest source is from DVC members who use thier points to cruise or for certain other non-DVC options. To get the cash to pay for those options, DVC sends the equivalent number of room nights over to the cash side. Without the ability to do this, DVC members would not be able to use thier points for anything but DVC resorts or exchanges via RCI.
2. If a DVC resort isn't entirely sold out yet, or if the Developer takes back points thorugh foreclosures, those points do not belong to DVC members. The Developer makes those rooms available to the general public and the proceeds belong to them.
3. If there are unreserved DVC rooms still available at the 60 day mark, DVC will send those over to the cash side. The proceeds (less a commisson to the reservations department) of any that are rented to the general public come back to DVC and are used to reduce DVC dues. You will see it on your annual statements under "breakage income". DVC members still have access to those rooms during that period, but they are competing with the general public for them on a first come, first served basis.
4. Disney retains a small percentage of the points for each resort, somewhere between 2% - 4%. While these rooms can be rented out for cash, they are mostly used for administrative purposes - for example, to take care of maintenence issues, or perhaps a booking error.
HTH. It's a common question that we all had when we were new.