Retail and real estate entrepreneurs are turning former big box stores into places where cottage industries can find customers.It’s a physical world response to what Etsy.com has done for home-based businesses nationwide since it launched in 2005 with a focus on handmade and vintage items.These general merchandise stores sell the same types of products and often use the old retail term “mercantile” or the more current one popularized by Amazon, “marketplace,” in their names.When you slap a name like mercantile on a store, “you can sell virtually anything, and we do,” said Clare Freeman, general manager of the Richardson Mercantile, a 55,000-square-foot store that used to be a Whole Foods Market in Richardson, Texas.