Hi....I've both rented FROM and then rented OUT points, and it is probably the easiest transaction you will ever do. The owner of the points always keeps final control over the points...meaning that he could cancel a reservation...but I have never heard of that happening (and I am sure he would be quickly banned from the dis, or at least, sounded thrashed!)
There's a fairly simple contract specifying who does what and when, and then I use (and I think most everyone else also uses) PayPal. I suggest that people put it on a credit card and pay for those charges...then if anything should go wrong,you can always have your CC back you up.
A cute story re renting out points to 'strangers' : the first couple I rented to, loved
DVC so much that they bought it and put me down as a referral. If I lived in a different state, I could have rec'd some cash back for that. The second couple that rented were there when I was there and we met and have been traveling together since!!!!!! We have 3 trips planned in August and September!!!!!
Of course, you have to be willing to trust and expect the best from people.
Disney does send you a confirmation letter. A recent 'rule' being more firmly adherred to is that member services will only speak to owners about any reservations, including those rented out. But a 3 way phone conference call takes care of that issue.
Whether you rent points or just a certain dollar amount per reservation, it is still much cheaper than renting through the Mouse (by half or more.)