Complete all scenarios with any character. After the ending sequence, you be given a new scenario to build a Megapolitan. You will have $200,000,000 to build it, with no rival leaving you free to build your own city.
Note: This procedure requires editing a game file; creating a backup copy of the file before proceeding is recommended. With a text editor, edit the "initialpref.lua" file in the scenario or level folder in the "scripts" directory in the game folder. Near the top should be the following entry:
if Game.GetDifficulty() == DIFFICULTY_(difficulty) then InitialValue.playermoney = (money to start with);
Find the difficulty you are playing under and change the initial value to whatever desired. Note: The custom scenarios in the game are in the "custom/deepred" folder.
To unlock every scenario, play the first game and build the following on Pacific Avenue: a theater, bar, restaurant, bakery, apartment complex, and clothes store. Build all of these buildings as tall as you can with a medium quality. It does not matter how much surface area you make them. You must do this before the second time period. Then, save and quit the game. When you restart the game, you should have all the scenarios unlocked and the budget will read 100,000,000, but will never decrease (unlimited budget).
Start an auction and save the game when the auction screen appears. Quit the game and reload your saved game. Usually the CPU players will pullout of the auction, allowing you to get the property for the cheapest price. If this does not happen, reload the game and try again.