A cliché statement I usually hear is the phrase it takes money to make money. My favorite concept is that ideas make money, or a variant from Mind of the Innovator is that it doesn’t necessarily cost money to solve a problem but ideas solve problems. The best time I see this in action is when I write. Sure, there are expenses in the act of writing such as electricity if I’m typing in a computer but the main point is the source of my writing—the usage of my brain—isn’t costing me any money. And it generates income, such as when I sell an article or submit a short story for publication. It’s also interesting for me that when it comes to residual income, one of the professions that frequently gets brought up is writing (of course your novel or book has to have been a big success in order for it to warrant residual income).