> So they want to sleep at your place but are not comfortable having you around?
Yes, this is extremely common. All of my in-laws would go in this category, more or less. I might spend the night at their house, but it would be awkward to wake up with them in the room. Many friends who have moved far away and I don't see them regularly any more would also qualify.
> And if they have back pain they can't sleep on just any mattress either
There is an enormous population that exists between "can't sleep comfortably on a couch" and "needs some specific kind of mattress."
> an entirely unused room
Space isn't at a premium where I live, a whole unused room is no big deal. Plus if I have a another child there is a room ready for them.
That's the source of a lot of guest rooms, they are rooms for future/past children. My own guest room is also an office when there aren't guests.
If a space is repurposed from a previous permanent use, sure. Although, nothing is free, it's a more reasonable situation to end up in.
But then we've also deviated from the discussion of acquiring things with the intend to perfectly cover an edge-cases. On-topic, that would be like getting a long-range car because you drive the 1000 km constantly rather than for trips, and later lose the need and only use the extra range for leisure.
> There is an enormous population that exists between "can't sleep comfortably on a couch" and "needs some specific kind of mattress."
I'm actually not sure there are many people in that group. I don't think there's far between a decent couch and an "eh" mattress, closing the gap of people that cannot sleep on one but can sleep on the other. A decent futon or fold-out bed also goes a long way, and to theorize a bit I expect those that would not be able to have acceptable sleep on such would not sleep well outside their own home and bed regardless.
Either way, futons or fold-out beds are quite reasonable propositions comfort-wise and I sure wouldn't consider providing more for friends and family that needs to sporadically stay over at my home.
Yes, this is extremely common. All of my in-laws would go in this category, more or less. I might spend the night at their house, but it would be awkward to wake up with them in the room. Many friends who have moved far away and I don't see them regularly any more would also qualify.
> And if they have back pain they can't sleep on just any mattress either
There is an enormous population that exists between "can't sleep comfortably on a couch" and "needs some specific kind of mattress."
> an entirely unused room
Space isn't at a premium where I live, a whole unused room is no big deal. Plus if I have a another child there is a room ready for them.
That's the source of a lot of guest rooms, they are rooms for future/past children. My own guest room is also an office when there aren't guests.