I think that you can put lets say 3 trailers on one lot. then you can add lets day 8 sims, different families, Now they will all be on one lot, so then you take lets say family A and put them in a trailer, you then click on the door and lock it to that family only. and then do the same with family B and C. I do think that will work, Now in RFLongs Haunted Valley, she has 5 or six trailers on one lot and you can place different families in each trailer. So it can be done.