Easy money

Buy Score Attack 3 in a shop, then go to arrange mode A and select Score Attack 3. Choose the Mosquito 02 (the blue jet) because it is much faster then Mosquito 01. You will die in the game will have unlimited lives. No matter what happens, keep pressing R and collect as much money as possible. At the end, return to the shop and check how much money was collected. If not enough, play it again until you get enough.