Understand that its a private transaction between you and the member.
People do get scammed - rarely, but it happens.
The bigger problem is likely to be in needing changes - even if the person you rent from offers to try and change your reservation if you need to, you should know that
DVC rooms tend to book well in advance and it can be VERY difficult to rebook on short notice - or even MONTHS out. Points expire, so it may not be possible for you to just move your trip. Even if your member offers to try and help, assume your reservation is non-refundable and cannot be changed. Get your own
trip insurance and be sure you are going to take this trip.
Understand that you are renting a timeshare, and that means some differences. DVC operates at high occupancy, so checkin might not be until late afternoon or even early evening. Check out is prompt - and there are no late checkouts.
Understand that the best value in rooms (like VAKL Value or BWV Standard) usually sell out FAST and usually aren't available for rentals. For near park resorts, you want to be planning a year out - reservations can be made eleven months out.