Steps:

1. Download required commerceDefinitions.xml from the links above
2. You will be replacing this commerceDefinitions.
   (Kindly read Fiddler’s Tutorial if it is not working for you. Too many dumb questions when the answer has already been answered thousands of times. Just read the tutorial if you do not know how to use Fiddler)

   REGEX:(?insx).*commerceDefinitions\.xml$

3. Once done, just clear cache and load Millionaire City.
4. Get the land ready then go and purchase the cheapest Commerce Building (Pizza). Roads must be connected!
5. You should gain a huge amount of exp and the game will go out of sync in bout a few seconds.
6. Refresh and you will gain back whatever money you spend on the building and STILL have the building there. Now, just destroy it and earn some easy money.
7. Once positive that the cheat works, buy the most EXPENSIVE commerce building that you can afford and repeat steps.