What is the source?

Across the street lives a family that I don't really know. The only thing I know about them is that they seem to always have something for sale. It started with a few bicycles in the yard for sale. This progressed into a weekly garage sale. I do not understand where all the stuff they are selling is coming from. They seem to have a never ending supply of furniture, clothing, tools, and assorted stuff. A great deal of it is new stuff like a flat panel mount and a dehumidifier. Many things are still in their original boxes. It just leaves me wondering what exactly is going on. I feel bad if they are selling everything to make ends meet. On the other hand I really don't want to live next to a perpetual garage sale. I am hoping that their supply of stuff is coming to them by honest means and isn't "falling off a truck" or something.