One of the most common question is in reguards to making fast money, especially at the beginning of the game. The 500 G you get at the start is just enough to purchase a few bags of seeds and that's about it.
Ship Wild Grasses
There are 10 fields in the valley and each one can sprout colored wild grasses every day. The grasses are 100 G or more a piece, and you're bound to find at least 10 a day.
Sell Casino Prizes
After Spring 08, you can unlock the Sprite Casino in the backroom of the Sprite Company Tree. You may have to exchange some of your Gold for Medals, but when you start earning more Medals via the card games you can spend the Medals on prizes. The cheapest item you can earn is the Teleport Stone for 1000 Medals, and then the Truth Bangle for 2000 Medals. Trade your Medals for the items and wait for Van to set up shop at the Inn on every 3rd and 8th day of the season. Van will give you about 5000 G for the Teleport Stone, and at least 11,000 G for the Truth Bangle! Once you sell them to Van they will reappear at the Casino, so you can repeat the process all over again. Even the Red Cloak for 65,535 Medals can be sold to Van for over 400,000 G.
In the girl version of HMDS, the Love Bangle, Truth Bangle, Red Cloak, Godhand, and Miracle Glove prizes can not be sold to Van. You can sell the Teleport Stone and Relaxtea Leaves though.
Save/Reload at the Excavation Site
If you take your Hoe to the ground inside the excavation site, you can find small bags of money (3 - 10 gold each) and jewelry that sells for 2000 G a piece. When you dig in the ground you exhaust your Stamina and get very few pieces of jewelry to sell for all the work you do.
To conserve your Stamina, enter the excavation site and then save your game. Start digging around until you find a piece of jewelry (Earrings, Broach, Bracelet, or Necklace), then reload your saved game. After you have reloaded just walk to the spot in the excavation site where you found the jewelry and dig it up with one hit of your Hoe. Then just save your game again, dig around until you find another piece, and reload just like before. Every time you exit the excavation site the items in the ground will reset. You could spend the whole day digging up little jewels of 2000 G and not exhaust yourself! You can also find Skin Lotion, Sunblock, Facial Pack, and Dress that sell for about 50 G each.
Sell fish to Van
Seems as though Van has a thing for small fish. Normally you can ship the fish for 50 G each to Thomas, but if you sell them to Van when he is in town you can earn about 250 G per fish!
If you feel that you just can't make enough money the normal way and you need to resort to exploiting bugs in the game, there are a few things you can do to earn a hefty profit.
1 Billion G glitch
During the winter season, hire the Fishing team to work at the Ocean. Each day they are working you have a chance of randomly being rewarded with 1 billion gold. You only have to check your Farm Assets screen to see if you have magically been gifted.
Sheering wool can be a tedious task if you're trying to unlock members of the red sprite team, but there is a cheat to clipping wool that will allow you infinite amounts of fuzzy goodness.
Both of these cheats have been corrected in the girl version of Harvest Moon DS. You will have to earn your money in Harvest Moon DS Cute the old fashion way; by actually farming.