HOUSTON, Texas -- Turning trash into treasure -- some retailers have been estimated to throw away $50 billion worth of merchandise a year. One Texan is taking their waste to the bank, making big bucks on dumpster diving.Matt Malone is what you'd call a professional "dumpster diver." He says he can bring in a considerable amount of cash on the side."I ended up making $100,000 in a year, as a part-timer," he said.He lives in Austin but travels the country to get some unique finds. He made a trip to Houston to show us his strategy.He stays away from restaurants and food trash. Malone's treasure trove lies behind big box stores like Home Depot, Office Max or Sears."When you take something back to a store, what do you think they're doing? Put it back on the shelf? Look on the shelves and tell me how many re-boxed or repackaged things (you see). Not many, so they throw them away," said Malone.Once they're tossed, Malone dives in.He inventories his finds and posts them for sale on sites like Amazon, eBay and Craigslist."Worst case scenario, you're having a yard sale," said Malone."I found an original Muhammad Ali painting that was done for a book by his daughter," said Malone of one of his most unique finds.On our adventure in Houston, he found a brand new table behind Pier One Imports. He also found computer speakers, a Dewalt cordless screwdriver, commercial grade LED lighting, credit card readers, and a Mac Classic 2 computer, which could sell for $100 or more on eBay.The biggest find was a brand new cherrywood desk with everything in the box. It retails for close to $300.Aside from products, Malone has come across personal information."I found Donald Trump's cell phone number. Someone had thrown away a Rolodex and it was a big wig obviously," said Malone.He was in Los Angeles at the time."We actually called Donald Trump. At the time, he wasn't the president," said Malone. "Uh, they basically told me not to call again."When we asked Malone if anyone had caught him in their business' dumpster, he said "yes.""I have no fear of that because it's public domain. It was a federal case that states it is public domain," he said.After making an inventory of everything, Malone estimates he can sell his Houston finds for a little over $3,000. Not bad for putting in a few hours of work.While Malone makes a lot of money with his dumpster diving side hustle, Waste Management, a refuse collection company, cautions against it.They sent us the following statement: