I found another unlimited money spot. It's found in the area to go to take the elevator down to Shantytown. It's only active after you've returned the tools and given the Vox Populi weapons. When you take the elevator back down to Shantytown, and then back up again, all the lootable areas will respawn, and the vending machines can be repeatedly possessed for money. At no point should you return to the gun shop, for then the doors leading to Shantytown will lock, and the player won't be able to go there again.