You can't have 2 households use the same rental lot at the same time. But, if you want to, you can send a household on vacation and put them in a rental. Then change households, send them on vacation and put that household in another rental in the same world. You can do that until you fill all the rental lots up. Then you will see members of all the households in that world that you sent there while you're playing one or the other but only one household will be playable. The games does that anyway when you go on vacation usually. I see other played households wandering around when I send one on vacation in Selvadorada and Granite Falls most of the time.
Hope this helps.
