When JoAnne Krupa heard Caesar Creek Markets was on fire last week, she said tears came to her eyes. “At first I thought it was my booth. I later found out it wasn’t in my area, but it worried me.

The United States has over 1,100 active flea markets with over 2 million vendors, pulling in $36.5 billion in sales annually. Thinking about getting started with this side hustle at your local flea ...