If you know anything well, a place, how to fix something, how to make something, how to do something, you can write a guide for it. You can sell your guide as an e-book, offer it as a download for a fee on your site or reach out to bloggers with similar content and ask if they will offer it as a paid download on their website (for a price of course).
When you create residual income, you are taking a step towards making extra money in a manner that does not require constant effort. The stream of income is actually generated from something specific; a specific effort that you put forth to create the stream of income opportunity in the first place. Residual income is not always a passive manner of making money.
Managerial accounting defines residual income in a corporate setting as the amount of leftover operating profit after all costs of capital used to generate the revenues have been paid. It is also considered the company's net operating income or the amount of profit that exceed its required rate of return. Residual income is normally used to assess the performance of a capital investment, team, department or business unit.