All new farmers will start their new lives on the island with only about 500 G to their name. That won't buy a whole lot, so it is important to know how to get some quick funds.
First you'll need to know how to earn money. There are two shipping boxes in the outdoor areas of the island; one on your own farm and one in front of Taro's house. To ship, place the item in one of your 4 tool slots, tap on the item to "hold" it above your head, and then slide your stylus towards the shipping bin. When you see a red down-arrow, you can release your stylus and your farmer will toss the item into the bin. Alternatively, you could just tap on the bin and then click Yes on the confirmation screen that comes up.
You can ship using either outdoor bin or any indoor bins you have Gannon build. Shipments are picked up at 5:00 pm every day and the money is directly placed into your assets screen. Items you place in the bin after 5:00 pm will be used for the next day's shipping.
The amount profit you earn for each item when you ship it via the shipping bins will depend on the item's Rank. The Ranks start from D (the lowest) to S (the highest).
The other way to make money is to sell items to Chen. Visit his shop on Saturday through Thursday and hold the item (or stack of items) in your hands when you tap on him. In his shop inventory you'll see an option called "Sell Item I'm Holding". The price Chen offers is fixed, regardless of the item's rank. He will not change his price if you talk to him a second time, like Van use to do in Harvest Moon DS.
The only advantage to Chen-selling is he will buy items that you can't ship through your shipping bin. You can sell him farm tools, seed bags, and even accessories. For anything else, you will earn more profit if you use your shipping bins.
The simplest way to earn money is to ship the wild grasses and flowers that appear daily around the island. All it requires is time for you to go and collect them. The items don't sell for much when compared to growing your own crops, but at least it's something!
Many people don't realize that the giant rock on the beach is more than just there for decoration. During the Spring season, a green film called Seaweed will grow on the rock. If you tap on the large rock you'll receive a jar of Seaweed, which you can toss in your shipping bin for around 800 to 1000 G a day, depending on the rank assigned to the Seaweed. Once Spring is over, you may no longer have a need for the Seaweed-crutch.
Another way to earn simple money is by going fishing. The fish and fish sizes you catch are random, so you may get lucky and catch a lot of Fish (L), or not so lucky and get stuck with a pile of Rubber Boots.
You won't start the game with a fishing rod, but if you give Taro gifts that he likes, then he will return the favor by giving you a free fishing rod.
Fishing in the Ocean area will earn you more money than anywhere else, especially in the Summer and Fall seasons. In the Summer you have a rare chance of catching a Pirate Treasure, which can sell for upwards of 30,000 G a piece! Fall season has Fish Fossils in the Ocean, and they can ship for, at most, 12,000 G a piece. The chances of catching these goodies are completely random and there isn't a best-time or worse-time of the day that might increase or decrease your chances.