Conolan wrapped the flea market information up in a nutshell. Thank you.
Here is a longer, more wordy explanation.
Ok, the flea market should be Sunday, January 25. Basically you visit your neighbors and walk into their house. They will tell you something like look around, touch something, etc. If you touch, let's say a couch, your neighbor will say whether it is for sale and how many bells. Then it is up to you to purchase.
When you are in your house, the neighbors will knock and then walk in. They will look at your furniture and ask how many bells. Only have out what you are willing to sell. Put everything else in your closet or dresser and then put that piece of furniture in your pocket.
I time traveled to Sunday, Jan. 25 the other day and this is what I discovered. So I went back to Jan. 22 and only put out the items I want to sell.
I guess I will see what happens. I will say this if your neighbor has a piece of furniture you need or want, they usually sell it cheaper than Nook. So make sure you have a lot of bells for Sunday.
Any corrections, please correct me. And enjoy the flea market event.