JOAN
New Leaf has a Stalk Market, which is similar to the stock market. On Sunday mornings you can buy turnips from a boar named Joan. Starting Monday, you can sell them at Re-Tail, but the sell price changes throughout the week. The changes in price may follow a pattern that allows you to predict when you can make the best profit, but there is always a risk of losing money. However, if the prices are good, you can make a lot of bells easily through the stalk market. This page explains the stalk market in detail.
Buying Turnips
Play the game between 6AM and noon on Sunday and look for Joan, a brown boar, wandering around your town. Talk to her to purchase turnips from her. Her price for the turnips will be between 90 and 110 bells. Her price doesn't change during the day. The turnips that you buy from her will spoil on 6AM the following Sunday.🌷Selling Turnips
To find out how much turnips are selling for in your town, go to Re-Tail and ask Reese for the current turnip selling price. The price changes when the Re-Tail shop opens for the day and changes again at noon, so be sure to check the price twice during the day to see both prices.🌷To sell the turnips, just sell them to Reese the way you sell other things to her. She will only buy them from you after the shop opens on Monday and before the shop closes after Saturday. You have to sell the turnips before 6AM on Sunday or they will spoil and you won't be able to sell them.
⚠️⚠️THIS WILL BE IMPORTANT⚠️
Risk of Losing Bells
Keep in mind that with the stalk market, there is always a risk of losing bells because you might get the Decreasing pattern, which will almost always be too low to give you a profit. The other patterns typically feature a price over 110 bells at least twice during the week, so if you track the stalk market each day and see any increasing price, you should be able to make a profit even if you miss a spike.