When bees appear from trees, take out your butterfly net and face the beehive. If you can catch a bee, you can sell it for $4500.
Place orange furniture to the north, green furniture to the south, yellow furniture to the west, and red furniture to the east part of your house.
Note: This trick requires a Game Boy Advance and a link cable. Play the game with the Game Boy Advance attached. Collect as much fruit as possible and travel all the way to the south. Go the pier at the beach. A Kappa will be there and will to bring you to a new island to the south. Get to the new island and drop all of your fruit. Return to the Kappa and leave. Transfer the island to the Game Boy Advance. On the Game Boy Advance, knock on the door to the house of the island animal. After it appears, move a piece of fruit in front of the animal. It will eat it and become happy. Keep repeating this until the animal drops money bags. Feed all your fruit to the animal, then put your Game Boy Advance on standby. Resume the game on the Gamecube. Go back to town, then return and talk to the Kappa again. Your game will now be updated with the Game Boy Advance data. Travel back to the island and collect the money bags.
Go around town with your shovel and hit every rock you can find. One of them should turn red when you hit it. Keep hitting it to get more money.
Every New Year your parents give you 10,000 bells. Change the system date on the Gamecube; or in the Animal Crossing options and change the date to the new year. Check the mail box and you will have 10,000 bells from your parents. Repeat the process, but change the year.
Dig for fossils every time you play. When the museum fills up with fossils, you can make a mint at Nook's or trade with residents for good items with fossils. Skulls of dinosaurs seem to be worth the most, usually bringing in 4,000 to 6,000.
Play the Stalk Market. Turnips do not seem like that much of a commodity, but its gold in the game. You can make a fortune buying Turnips and selling them at the right price.