OK, I'll try to answer this as best I can.
First,
DVC owners have a 'home' resort. This home resort means that you can book at that resort at 11 months prior to your stay. So, if you want to book now for a 9/04 stay, owners at BCV could book for you. All other DVC members can book their 'non-home' resort at 7 months prior, so could do it for you starting in February.
As for the cost, it's almost guaranteed to be the cheapest way to book it, and so, welcome to the secret of renting DVC points! As a side benefit, you'll find that the accomodations are typically 'better' than Disney hotel rooms. You don't get normal cleanup service every day, but instead get a full kitchen and Jacuzzi in rooms one bedroom and larger. In a studio, you get a limited pantry area. Once you've stayed in a DVC one, two or three bedroom villa, you'll be spoiled and settle for nothing less every time you go.
As for payment, you could pay for a stay by credit card if you use something like Paypal. Keep in mind, this will cost the member 3%, so expect them to charge you an additional 3% over the normal rate. Points go for $10/point on average, so you should expect to pay $1040 for your stay if you pay by Paypal bank account transfer, or check. If you pay by Paypal via credit card, add an additional $31 or so to it. It'll still be cheaper than booking with Disney direct.
As for it being available, you'll have to check with the member that you want to rent the points from. You tell them what you are looking for (room type, resort, dates), and they'll call DVC Member services to check availability. If it's available, they'll tell you, and you can finalize the deal. I did this and booked a 2 bedroom villa at Old Key West by renting points last year. It was far cheaper than Disney direct, and was very very impressive. In fact, my wife and I decided to buy into DVC after that trip, and now own 150 points at BCV.
That brings me to my last point. Unlike most timeshares, we are not 'tied' to certain week(s). We simply have points which can be used similar to cash according to the rate schedule (DVC Member Guide Point Schedule) for the individual resorts & times of year. Again, at your home resort you can book at 11 months out, 7 months at all the others.
And, if you're wondering about the safety of trusting a DVC member with your money (they'll probably want full payment as soon as possible), don't. It's a lot more risky for the owner, not the renter. DVC owners are primarily mid to upper middle class family folks (Yes everyone, I know there are exceptions...) who simply want cheaper vacations. They are not scammers who'll want to take your money. Everyone who own probably spent > $10k to buy into this, and are not the kinds of folks you should worry about.
That's my $0.10, so good luck.
