DVC is a point-based program. You purchase X number of points and spend them how you wish. You'll get a book with the number of points required to reserve at each resort at each time of year. You will pay association fees on your property. You may reserve a stay at the resort you own 11 months before your stay, and you may reserve a stay at any other DVC resort 7 months before your stay. You may bank your points for one year. You may borrow from one year in advance. In essence, if I banked last year's points (not happening), and I chose to borrow the points from 2007, I would have the equivalent of three year's worth of points for a trip this year. Then, if I chose to travel next year, I could borrow points from 2008, but that's a nasty cycle that ends in add-ons. (Add-ons are additional contracts with more points to help the Disney addicted get their fix.) You have a use-year, which is basically the month that your DVC year ends and begins. You must have your points banked or used up by this day, or they will expire. All DVC contracts expire after a certain length of time, which I can't remember at this moment (sorry) but seems to me to be something like 50 years from the opening date of the resort. This is a very simplified explanation, but I think it's good for basics.
DVC is a luxury resort, so I don't think there's any way it can be considered a savings if you normally stay at a value resort. Just like you'd pay a lot more for a room at a deluxe resort, you'll pay more for DVC than you will for a value room.
However, some things to consider are: Would you **like** to stay at a luxury resort, if you could afford it? Would it be a big convenience to you to have a kitchen and/or a washer and dryer available to you? Would you appreciate having the extra room available in a villa? How important would these things be to you?
I second the notion of taking a tour. It can't hurt, you'll get some specific answers to your questions, and they are *not* meant to be high pressure. If your guide pressures you, they're doing their job wrong, and I would ask for a new one.