luiginumberone

Without an Action Replay, the main way to get money is to sell things. And without selling things, there really is no way to get "high amounts of money." However, there are some alternate ways to get small amounts of money:

Shake trees. Unless you've cut down all your trees, of course. Walk up to one with no item in your hands and press A to shake trees. If you shake fruit trees, you get fruit, and you have to sell it. But if you shake non-fruit trees, you get one of three things. Nothing, Bells, or lots of bees.

Run errands. Every once in a while, while talking to a neighbor, they will ask you to deliver something; a letter, package, or something similar. Make sure your pockets and letters have one empty spot, then accept. Deliver and come back, and you'll get something. Sometimes it'll be Bells, sometimes furniture or stuff like that. Unfortunately, you'll never know until you deliver the thing.

Interact with neighbors. Sometimes, your neighbors will challenge you to contests, or drop hints about something they want. If you can beat their challenge, or give them what they want, sometimes they'll give you Bells.

Search for the money rock. In every town there are rocks. And every day there is a money rock. Equip your shovel and walk up to every rock in your town. Dig a hole behind you to make sure you don't back away from the rock. Then, press A to hit the rock. If nothing happens...fill in the hole and move on to the next one. If money falls out, quickly tap the A button until no more money comes out. This actually is a high amount of money, but you can only do it once a day.