An NPC is created, who is a gambler, or better yet, a number of NPCs who gamble. These can take the form of a few people on a small boat near the river or something of the sort.
The person chooses the amount to bet (similar to buying a product from a vendor) and then plays the game with the NPC
Double or Nothing: The NPC Rps flipping a coin, and the player either wins (gets double the money) or loses (loses the money). If the chance to win is at 40% or so, it'll still be similar to a real coin, but would allow a net loss and .: a money drain.
Card Game: Again a bet is placed, but this time if a person wins (gets that 40%
I believe something like this would be interesting. Discuss.