"Supply and demand, my friend. Supply and demand." -Vendorman on Market Principle
Finding a Shop
You thought spending money was hard enough? You're clearly playing the wrong game, pal. On the second level of every area, a second secret exit is hidden somewhere. It's hidden better than the regular exit, and rather than use the area-standard door design, it is decorated in flashy neon and velvet.
Once getting there is out of the way, you will be greeted with a small room. At the opposite end of the room is a counter with a random shopkeeper sat at it. The shopkeeper will be picked at random from the pool of NPCs designated to keep shops. The items in stock will be randomized as well, most picked from the current area's accessible items and rarely some will be from the next area.
Once you have finished spending your hard-earned cash, you may exit through a door in the back and go to the third level of whatever area you were in.