I also rented points from a DCV member.
It is not 100% safe - you will be taking a risk (which is really hard for me to do, so I understand your hesitancy).
What COULD happen? Here are the worst possibilities: the DCV "member" (they could say they are one and not be) could take your money and not make a reservation, could take your money - make a reservation but then cancel it at any time, could take your money - not pay their annual dues and then your reservation would be subject to being cancelled.
What I did was a Search (like Cat said) of the person offering to sell points - the person I bought from had a history here on the DIS with over 200 posts - I read many of these to get a feeling for who that person is, then I offered to "make a deal".
The person I delt with wanted a bank check - I sent it before I had the reservation number. Although everything has worked out fine (received the confirmation,they wrote me a "receipt", etc...) - in retrospect, I would have felt more comfortable if we had a written agreement between us before the transaction was made (like "I agree to pay, you agree to make and keep reservation, etc... - signed by both parties, etc..) I would think something in writing would make everyone feel better. I know that some people DO offer an "agreement paper" but most do not. You can PM me and I'll give you the name of someone else who offered an agreement (they didn't have points at the resort I wanted so I didn't end up working with them).
Sorry this is so long, just do a SEARCH and see what you can come up with. It is a great way to save money on a reservation - and I've never read any "deals gone bad" posts here on the DIS - you can be sure though that if it does happen, we'll all hear about it. Good luck.