I’ve been renting my Disney Vacation Club points out for 20 years and Marriott DC points out for 5 years. I have never rented one point that I’m not paid for in advance. It’s been my policy since the beginning when a DVC renter asked to pay me in increments. I never did that again! I had to chase her for the balance and I didn’t enjoy doing that!
As far as owner transfers within Marriott, I always ask for payment in full. Once payment, and other renter information, is gathered I make a three way phone call with Marriott and transfer the points. I’ve never ever had a problem and I will continue to do business this way.