I remember that some of my friends were starting to sell used catalytic converters. They told me that it is very profitable, around 500-600$ for one piece. I was very interested in making some cash because I had an old Cadillac in my backyard. But, I found an offer on https://www.scrapi.com/scrap-car-calculator. It was more attractive than my friend's one. I got the money very fast in my bank account. Also, the next day two guys came and took it away from me. In this way, I saved a lot of time, made some money, and got rid of something old.