The easiest way to make truly passive income is to invest your money into a stock, ETF, mutual funds, etc. The richest people tend to get even richer because they consistently invest and reinvest their money. Keep it up, and you might even be able to never have to work again. I know one guy whose investments now earn roughly $50,000 a year in dividends, and so he is free to live without working if he so chooses.
One of the most appealing options, particularly for millennials, would be #12 on your list (create a Blog/Youtube channel). The videos can be about anything that interests you, from your daily makeup routine (with affiliate links to the products you use), recipes (what you eat each day) or as you mention, instructional videos (again with affiliate links to the products you use). Once you gain a large following and viewership, you can earn via Adsense on YouTube.
Cultivate little-known DIY projects and ideas that are needed by consumers. For example, provide tips and tricks on self-improvement or weight loss. Develop your website to cater to the type of information you want to sell. Build your e-mail newsletters at the same time and up-sell a monthly subscription. You will have effectively rolled three services into one great profit.
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.