Scrap metal. I always leave my scrap metal out on trash day next to the trash can. A guy in a pickup will come around and get it. I would have to save it up for years for it to be worth a single trip, but he’s getting a full load or two every day. I’m sure I’ve lost out on a few hundred bucks over the years.
I’m sure if you started an electronics recycling company or a clean out business you could get people to pay you to take their stuff.
There’s quite a few different YouTube channels dedicated to finding scrap metal or even a guy who owns a scrap metal business who pays for scrap metal, processes it, then sells it to various foundries to be melted down into something new.
I personally like to buy used items and resell them on eBay. Sometimes at thrift stores, but also garage sales and estate auctions. You can find auctions nearby on a site called hibid. I also sell my old unused items on eBay as well or even parts from broken items. Just look up the item on eBay and filter by sold.