I am a TUG member and have rented several Timeshare units with no problems, getting great rates. That being said, there can always be a bad apple in any group. I would talk to the person on the phone. If you feel comfortable, move forward. Otherwise walk away. If your travel is within 90 days, you can pay them via a credit card on paypal and receive some protection from your credit card company if they will reimburse you if you have problems with your purchase (of course that doesn't help if you show up with no room).
A DVC member will have to make all reservations, dining plan and magical express reservations for you, but can send you and email with a link to the disney site to see your reservation. If the DVC member owns one of the Florida DVCs as their home resort (not Hilton Head or Hawaii), then their names will be on the Orange County deed website to verify ownership.
If it is a rental of an RCI exchange (which is not technically permissible, but happens all the time and I won't go into whether it should happen or not), then there will be a $95 charge payable to the resort when you check in. However, once they do a guest certificate in your name, you will be able to call DVC directly and add your other guests, book the magical express, etc.
I am a DVC owner, Tug and RCI member. If you have any questions, pm me and I can give you my opinion if the deal seems legit.
Good luck! Enjoy your trip.
