Both people in the transaction have trust issues (if the person getting the transfer has to pay up front, how does he/she know the person doing the transfer will/can actually transfer the points?)--so requiring payment up front helps the person doing the transfer but doesn't help the person getting the transfer at all.
Probably better to take the time to establish a relationship and build some trust.
I have someone (from here on the DIS) who I go to whenever I need extra points (rent or transfer), and he knows he can come to me should he need extra points in any given year.
We exchange occasional emails; have each other's addresses and phone numbers--in short, we "know" each other.
So, when it comes time to rent/transfer, neither of us worries a bit about the transaction going smoothly.
Because these are all person-to-person transactions, it makes a lot of sense to invest the time in creating a "real (even if it's cyber) relationship"...