From your post, these people are not even close enough for a one night sleepover. It's your home and you shouldn't let anyone take advantage. If they haven't been invited, this is a barefaced imposition on their part!
Clearly your house is not a hotel! How well do you even know these people? Would they go out of their way to show some appreciation afterward? Have they even offered to share for extra groceries, water, heating and electrical? What about housekeeping and laundry services?
You may want to suggest that they move to a hotel 'efficiency' suite. If they still don't get the hint, tell them outright that the proposed arrangement may work well for them, but it doesn't work for you. You don't owe them anymore explanations. Above all, do what you want, NOT what they want.
They won't like it? Better they get upset for a few minutes instead of you being upset for a long, long time.