There is no such way to reach "infinite gold" in Kingdoms at War. All games have programming to a certain point, after that point in the game is reached (Talking about how much $ you have out at once) you are screwed. Either you just don't gain money, you get intense lag/crashing, or you hit the kill screen (if possible). Please note that that point has not knowingly been reached, and probably will not for a long time.