There is multiple ways to obtain bells within animal Animal Crossing: New Leaf and this page will go over a few methods
to obtain bells in the fastest ways.
Selling Fruit
Fruit trees are common within your animal crossing town, and your town will contain one of the fruit:
From top line left to right:
This is random and can be any rock that is in your town. To obtain the bells from the bell rock, make sure to repeately hit it and bells wil fall out. You can usually get max 8 stacks of bells from one single rock, and the amount in the bell stack will increase with every hit, upto 8000. If you fail to repeeatly hit it, it will stop dropping bells. Reminder this resets daily.
A rock can also be smashed and drop an ore, and this ore can be sold at ReTail for a profit.
There are also many other ways to obtain bellls in new leaf, but these are some of the main and quickest ones!