This really helped me.
Set your town time and DS time to 01.01.2000 and put in 10,000+ bells.
Then save your game and switch of your DS. Turn your DS back on and change the date to 01.01.2011. Then go on Animal Crossing and check your mail. (You should have cleared out your mailbox first for at least 4 spaces) In the mail you might have 10,000 bells from your mum AND a letter from the town hall saying you have some interest of 6,000+ bells. Then save your game and turn of your DS again. Set your DS time to 01.01.2022. Then play on Animal Crossing and check your mail again. And you will have another letter from the town hall saying you have interest. You can do this as many times as you want, but don't go as high as 2099. The interest you get every time you do this will be more, until it gets to 99,999 bells at a time.
With this you will be able to unlock the following items after some time:
Box of Tissues
Piggy bank
Pelly's pic
Phyllis's pic
Town hall model
WARNING: You get loads of weeds and neighbours may change. (Mine did.)
CAUTION: YOU'LL BE A MILLIONARE!