When you run out of all your gold and all the npcs come and ask if you you'd like to sell items or give souls for gold, hitting the no button multiple times doesn't have any negative effects at all aside from not being able to have gold until you eventually say yes. (Also theres a knight that will just give you a treasure chest if you rng him) Though there is no downside to this method at all. My population keeps growing and growing and the city expands with each passing day even though our kingdom is broke.
I kind of wish there was a downside to being broke for a set amount of days like your kingdom becomes poor and decreases the population as time goes on or something like that.
More of a suggestion if anything I just thought id post about it :O!