Required Tools:Cheat Engine
1. Enter Millionaire City [http://apps.facebook.com/millionairecity/
2. Open Cheat Engine.
3. Select browser in process list.
4. Surround ONE townhouse luxury with coffee houses. This is to ensure that you will not exceed the coins limit and get a game error.
5. Scan 100000 in Cheat Engine
6. A few addresses returned. Select all those that end with 4C and press the red arrow
7. Change all the C to 8 until you find the address with a value of 45
8. Change 45 to 45000.
9. Now wait till your coffee houses can collect $$ and watch as you earn thousands of coins instead of a few hundred. Just set a lot of coffee houses around 1 house and set a mouse recorder to click on the coffee houses and leave it to bot and you will be extremely rich.
10. Watch my video if you are unclear.
I didn't really test out the max limit of coins that you can gain before getting an error, but as shown in my video, $275,400 is a safe number that will 100% save.