First You Need To Be Able To Have a Fruit Other Than Your Town Fruit. 
Plant this Fruit Loads of Times, So You've Got Loads of Fruit trees That Are Different
from Your Town's, eg. If Your town grows apples then you have to plant loads of different
fruit like oranges or something. Now you've got loads of orange trees right? Fruit that
isnt from your town sells for 500 right? So now you can sell all the oranges after youve
picked them off the trees, Easy Money! Awwh damn so now theyve run out right? Do Not
Worry, Save Your Game Then Re-on it to Go To Your Ds Settings, Change the  date so its a
week ahead or something. Now go on animal crossing, as soon as its on save the game
outside your house, Now change your settings back to normal, WAHOO!!!!! More Trees To Pick
From!

Please Thumbs Up If This Helped!