The most profitable items are those you find undervalued. For instance, I recently discovered a diver's compass at a garage sale for $5.00. I knew nothing about it but in my estimation and a brief discussion with the person who was selling it, determined it still worked. The person also explained it was expensive when she bought it. She was no longer involved in diving and getting rid of it. I bought it not sure, yet believing it was at one time expensive. When I got home, I discovered the item was selling for $500 plus. Not knowing anything about it I began to list it as working guaranteed at $99.00 It sold for $240. I sent it off and communicated with the buyer to be sure it worked. It did require a new battery. Had I actually tested it and put in a new battery, my price would have been higher. Understanding what is undervalued is the best items to sell as they will have the most interest and command a higher price with the most profit possible.