I have rented points (reservations) several times to cover costs of non Disney cruises and airfare/tickets for DL trips. I have been fortunate in that the people I have rented to have been very nice and paid promptly. I ask for payment in full when they get the confirmation letter for the reservation (which is sent to me and then I forward it). I have made it a point to spell everything out very clearly so there are no misunderstandings between me and the person I rent to. For example:
1. payment in full at confirmatin
2. no refunds but I will work with them if they need to change the reservation or cancel it subject to availability.
3. I explain about no daily mousekeeping, that they can do ME and
DDP but that I need to make the arrangements for those and that they cannot check on their reservation with MS.
I do not do a formal written contract just email and phone conversations.
I have only done this through this site and once rented to a person where I worked and have had good results. with only one person asking me to make the reservation and then saying - "oh no I just wanted you to check availabiity and now we can't go then". Since I didn' ask for a deposit prior to making the reservation as some do it was my mistake however I just cancelled it. You may find someone who is putting together a family reunion that will need a large number of points. I might consider a partial payment at confirmation and specified payments later if it was someone looking for 300 or more points at once. You need to require payment prior to any dates where you could get stuck not being able to bank or use the points if they did not pay and you have to cancel.
Read the faqs on the rent/trade board and you should have no problems if you
follow the sugggestions you will get there.
Good luck and hope you enjoy your cruise.