To unlock the Big Money cheat, save your game. Open the "Baldur.ini" file which is in the game directory in your text editor. Add the line "Cheats=1" under the "[Game Options]" heading. Then, start the game and press Ctrl + Tab to display the console window. Enter one of the following codes, press Enter, then press Ctrl + Tab to close the console window and activate the corresponding cheat function.
CLUAConsole:AddGold("999999999")