The flea market gives you a chance to by your villagers' stuff and sell your stuff to them.
What is the Flea Market?
The flea market is a special event where you can ask to buy other villagers' furniture, and they can ask to buy yours. You are allowed to set the price for how much you are willing to sell the furniture for, but the villagers might not want to pay the amount that you're asking. Similarly, villagers will set the price that they want to get in exchange for their furniture. Sometimes you won't be able to get the deals that you want at the flea market, but it's worth a try.
When is the flea market?
It occurs on the first Saturday of a few specific months. It starts at 6AM and lasts until 6AM the next day.
Where to go to sell your items
To sell items, just stay in the main room of your house, and throughout the day you will get random visits from villagers in your town. Every villager will come to your house, but each villager only visits once. Every character that you have in your game will get one visit from a villager on Flea Market day. But if a villager is sick, or in the process of moving in or out, then that villager will not participate.
How to Prepare before the Flea Market
The villager will only try to buy things from the main room in your house, so before the flea market, you should consider removing the furniture items from the main room that you do not want to sell.
How to sell things for high prices
The maximum that a villager will pay for an item is three times the sale price, but this depends on how good your friendship is with each villager. If you do not have a good relationship with a villager, you will not be able to sell your items for that much.
How to sell more than three things
Normally, a villager will stop buying stuff after buying three things. But you can make the villager buy more things if you leave the main room and come back again. However, this only works if you have had at least one expansion to your house. It won't work if you go into the attic.
What should I sell?
Animals are attracted to more rare and expensive items. Fossils are often a good choice.
What can I buy from villagers?
If you go into an animal's house, and that villager tells you that he or she is selling stuff for the flea market, that means that you can tap on any furniture item in the room and ask if you can buy it. Sometimes the villager will say no, but you can exit and try again, and the villager might decide to sell it to you after all. But sometimes there are items in a villager's house that the villager will not sell to you, no matter what. Villagers can have very rare items in their houses, like Spotlight items, so don't miss the opportunity to get a rare item!