First off, your guide is decent, because this does help, going back and completely destroying towns. But in fact it is not the most effective way. Just as a tip I'll let you know that by playing the level in Russia called Secret Base 2 you wiill gain the most money per level. That level makes the most because of the amount of people, as well as the huge airplane that explodes with coins. All levels with a lot of people are good, but through my testing i figured out Secret Base 2 is the best. Happy Gaming!
Haha apparently. But go with my suggestion if you are able to beat Secret Base 2. It loads you up with a lot of coins. I haven't played in a while but if i remember correctly it was somewhere near 12 000-16 000.
