Y – You Owe – fines, taxes, tariffs, fees, tolls, etc.
If a living city, where are the points where the government or local gang imposes fees for its services?
If a fallen city that is now occupied by new inhabitants, do they impose taxes and fees? If inhabited by ogres, they will just take all your stuff as the fee, as will most other humanoids and intelligent monsters. The ones that don’t eat you, will likely enslave you, or just kill you for the sport of it.
Intelligent monsters might impose exorbitant fees on passing caravans to let them pass mostly unharmed. This would affect the price and availability of certain goods.
If the city is not fallen, how far beyond the city walls to taxes and fees begin to be imposed? Is there a fee for every bridge and ferry, beyond the operator’s base fee? Are their toll booths at key locations along the road? If you have never had to pay a fee to cross a bridge or to drive on a tollway, this concept might be foreign to you. The AD&D DMG has a good overview on this. If the PC’s hang around civilization, they will run into lots of taxes and fees, which might induce them to go seek further fortunes.
For fallen cities, will random coins be found periodically near abandoned toll booths? Will the coin box be lost and found in some random location?
Will a tax collector have a hidden stash of his share, legal or illicit? In the ancient world, taxes were collected by tax farmers who bid how much they could collect, and they got to keep what they collected beyond that point, thus making them quite disliked by the taxpayers.