Here's an idea for the money issue:
A Bank.
This will keep track of what the citizen's have, and if they lent/gifted/donated money to anyone else.
Also, (mostly in the next demogame) have an economic system for pre-currency (bartering), pre-economics (just currency, and no 'true banking system', and post-economics (modern banking). Stock Markets would get a bit complicated.
Bartering - In effect until currency. Citizens have a X amount of supplies (food, crafts, clothing, etc.), and trade them at the town square. There will be no standards. In other words, one person might feel that 1 house is worth 500 melons, and 200 articles of clothes, whereas another might see 250 horses, 100 melons, and 500 of a certain craft (jewelery, toys, etc.) as being enough.
Currency - A normal exchange of coin. This is where the user will get GPT. It's a very simple system, with no banking.
Bank - Users can store their money (gain interest), or get loans for say, a house.