when you rent, you still get onsite perks like free parking at the parks, delivery of park purchases to your resort, bus service from the airport, extra magic hours and access to the DDP.
when you rent, you do not own the reservation and disney will generally not deal with you directly about the reservation, so you would need to go through the owner in advance to add the DDP. the owner would need to add it (and make payment at that time) at least 48 hours in advance, which means you would need to let the owner know well in advance of that.