The 3rd Amendment to the US Constitution states:
No Soldier shall, in time of peace be quartered in any house, without the consent of the Owner, nor in time of war, but in a manner to be prescribed by law.
It makes me wonder what the conditions must have been like in colonial America that this protection was important enough to be third on the Bill of Rights. And more importantly, I wonder how those conditions relate to our fantasy worlds. Since the standard D&D world draws a lot from the Middle Ages, it’s plausible that quartering troops in people’s homes is a regular practice.
Since D&D characters often act as mercenaries or direct agents of a lawful authority (church, king, baron, etc), they might be the “Soliders” discussed in the amendemnt. To me, that implies in a pre-3rd Amendement world, when acting as lawful agents, PCs can demand food and shelter from citizens. That is a great way for PCs to save the 5sp for a night in an inn’s common room and get a hot meal to boot.
As a bonus to the characters, if a homeowner is going to let you sleep in his barn or guest room, he’ll probably roll over if you requisition his horse, weapons, or other goods needed in pursuit of your service. After all, who is he going to complain to? You’re working for the authorities. (It might be interesting to try this in a land where your organization is not recognized or treated with hostility).
On the flip-side, PCs may be asked (or required) to provide accommodation for NPCs, especially for those higher ranking in the characters’ organizations. This could mean giving up their rooms at the inn all the way to turning over magical gear! When that happens, your characters should begrudgingly give them over and then you should remind your DM at every opportunity that he owes you one!