Each year there a 2 helpful events that can help you get money:
Easter
Halloween
The furniture claimed from these events sell for high prices and because of this I have managed to get lots of cool stuff for my character.
Easter
At easter Zipper T runs a digging contest where your character can dig for Bunny Eggs.
I apologise for the pictures bein blurry but I couldn't find any others and my SD card is not working.
Once you have dug up the eggs they can be opened. If you get a Token give it to Zipper T and he will give you furniture. The highest selling item I found is the egg bed. It sold for 45,000 bells.
Get the complete set of the furniture and it qualifies for every theme given by the HRA.
Halloween
At halloween you will find that all but 3 of your town members will be out and about at night dressed as Jack. Your challenge is to find the real Jack and give him candy that you will obtain from the 3 townmembers by talking to them in their houses.
The way to tell them appart is to walk quite close to a 'Jack' but not too close and see if they run towards you. If they do RUN!! it's a townmember who will take your candy from you. If not, go closer, it's Jack.
If a townmember does manage to catch you tell them you won't give them candy and they will swap a piece for a Jack-in-the-box. The Jack-in-the-box sells for more than the candy.
The furniture Jack gives you should sell for a high price.