The term “residual income” refers to the income that someone makes after their work has already been completed. An example of residual income is the earnings an author continues to make on a book after it has been published, when fans continue to purchase copies years later. Residual income is ideal because it is money that is being earned while doing nothing in the present moment to earn that money.
As a person that reads blogs I love it when people add affiliate links of the products they’re talking about because I don’t have to search for them. For example, when I’m deciding which crafts I’ll make with my kids it saves me a lot of time to click on the affiliate links of the products so you’re helping out your reader as well as making side income. See here how I link to products in crafts.

"The majority of people I see who are interested in passive income and pursuing it, haven't learned how to create value in the first place. They're just trying to do gimmicks and tricks and formulas. They're trying to do the automation part, but they've missed the point that the automation only spits off cash if it's based first on automating something that actually creates value. If you automate something that is worthless---or worse than worthless, a scam -- it's not going to work in the long run."
As you can see, I linked the word PDF with a tool that could help readers if they had the same problems, thus giving them a way for them to solve the same problem if they had it, while earning money from their downloads and in-app purchases. I haven’t actually placed my referral link as this is an educational article, but the principle is the same. That link doesn’t have to be an app, it can also be a page on Amazon, or a link towards some other online store that offers commission for affiliated sales.
In all reality, any business that involves selling a product is passive in some way. I mean, once the product is developed and created, you’re not actively creating it anymore; rather, you stand back and watch as people buy it and your bank account grows. But when you hear people talk about online passive income, they’re referring to a specific kind of business and specific kinds of products.

​I’ve been into home décor lately and I had to turn to Etsy to find exactly what I wanted. I ended up purchasing digital files of the artwork I wanted printed out! The seller had made a bunch of wall art, digitized, and listed it on Etsy for instant download. There are other popular digital files on Etsy as well such as monthly planners. If you’re into graphic design this could be an amazing passive income idea for you.

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.
Almost all of these ideas require starting a personal blog or website. But the great thing about that is that it's incredibly cheap to do. We recommend using Bluehost to get started. You get a free domain name and hosting starts at just $2.95 per month - a deal that you won't find many other places online! You can afford that to start building a passive income stream.
Now that we've found how to compute residual income, we must now use this information to formulate a true value estimate for a firm. Like other absolute valuation approaches, the concept of discounting future earnings is put to use in residual income modeling as well. The intrinsic, or fair value, of a company's stock using the residual income approach, can be broken down into its book value and the present values of its expected future residual incomes, as illustrated in the formula below.

The topic of buying and selling blogs deserves it’s own book though and is a very difficult skill to master I must say.  I rant about the greatness and simultaneous pitfalls of marketplaces like Flippa elsewhere on this site, but needless to say I think this is it’s own expertise; worth learning more about for a lot of us who know that starting a business (getting momentum) is a lot tougher than fixing up and steering an existing business to greater profits (maintaining and directing momentum).