Three years ago, Glen Zubia was stuck under a mountain of student loan debt, living with his parents and struggling to scrape together car payments. Now, the year-old has his own four-bedroom house in El Paso, Texas. He even co-hosts a weekly podcast where he tells listeners all about how he turned his finances. Zubia is a master of passive income through print on demanda system in which designers link up with sites like Amazon, Teespring and Redbubble to sell shirts and other items. Companies handle the production and customer service while paying out royalties, meaning people like Zubia can earn big without much investment or upkeep. Zubia is no stranger to making money off of the internet. While he was in college, he sold custom action figures on eBay; while trying to pay off credit cards, he tried writing books through Kindle Direct Publishing. But in his fourth month, he got a check. He used Adobe Illustrator on his iMac to crank out a catalogue of 2, designs — a process that invo...