There are times where the Shop will result in a decrease in GP as well. but its usually only something from -100 to -500 GP so nothing to really worry aboutShops are available in the shop (sounds funny, but it's true, lol). You use it like you would use any toy/item.
Your character will then appear in the shop for a few seconds and if you make earnings, your GPs will increase - though at times your character will appear sad if they don't earn anything. This is completely random.