Each town person has a debt and a credit.Town net debt -...

Each town person has a debt and a credit.

Town net debt - $0.

Innkeeper gets tennant, who provides revenue (which can't be recognised until the room has been used) and cash, which is a prepayment.

Innkeeper takes cash and the cycle removes all the debts and credits.

Innkeeper winds up with the note. When traveler leaves, innkeeper looses the revenue and so gives back the $100.

Town net debt, $0.

Could also have been achieved by each person selling their credit to their debtor.

Ain't double entry accounting exciting?