The craziest part of this was I’d wake up in the morning and there would be more money in my bank account, from people who had bought my book overnight. When you think about it, an online store that sells something that’s digital is something that’s open 24 hours a day, 7 days a week, 365 days a year. Using tools, software and systems, you can automate the delivery process so you literally don’t have to do anything to serve that audience. That’s super powerful.
Can you expound on the use of publicly-traded REITs as a passive income source? I’m 31 years old. No children. No wife. No dependents. (I am the closest thing to Ebenezer Scrooge you’ll ever see). My monthly expenses amount to less than $2,000 per month (most of which go to pay student loans) . I have a decent job making over $55K per year. I also have a $60K inheritance coming my way in a few weeks. I am absolutely crazy about achieving absolute financial independence, which for me would require a passive income of over $2000/month to cover my living expenses. I could achieve that in a mere couple of years if I were to save excessively and dump my savings (and inheritance) into a Mortgage REIT via the stock market, most of which are shelling out above 10% returns in dividend payments. Is this a good strategy for me? Or am I being too hasty and assuming too much risk?
The reason I consider dividends artificial and believe they don’t matter is because you can just as easily reinvest your dividends. If a stock is worth $100/share, I don’t care if it issues a $1/share dividend or if the share price instead increases to $101/share – either way, I have the same amount of money, because there’s no difference to my net worth whether I take the dividend or sell part of a stock. 

You know the fantasy: write some ebook (or better yet, hire freelancers in Mumbai to research and write it for you at $.20/word!) on some niche topic, set up AdWords and Facebook campaigns targeted to the right keywords (you can hire those Mumbai guys to do your keyword research too), put up a cheap landing page (with copy written by... guess who!), press "Go!" on the PPC campaign, and voilà. . . just wait for the money to roll in while you sleep!
This is the best post I’ve seen on passive income streams. I’m similar to you in that I worked in IBanking for a few years but wanted out. My approach is a little different, instead of starting with the CD’s, I’m trying to build up my net worth with riskier asset classes such as stocks and real estate to get the benefit of compounding. Then, as I approach my retirement year goal, I’ll start moving them into CD and bond ladders. In theory at least, it’s best to have the highest net worth just before retirement, then convert them to risk free passive income. You’re method is more patient and probably more practical than mine. I guess I’m willing to take more risks.

Real estate has another perk: Tax law in the US (and most countries) has been written by landowners. There are some ridiculous loopholes, like the ability to deduct expenses (and maybe even some interest) as a cost of doing business. Also, you can sell the property and buy another one without paying taxes. I won’t go into detail here, but Real Estate is my favorite form of passive income, and it makes up over 50% of my portfolio. See the next section for a breakdown.

Purchase the rights to royalties. Royalties are payments made for the use or sale of intellectual property, like a song, book, or trademarked product. These royalties are paid from the seller of the property to its creator. You can earn royalty payments either by creating the intellectual property yourself or by buying royalty rights from someone else. In the latter case, you can buy the rights for a lump sum and then receive regular royalty payments that will eventually return you your initial investment.[3]

This encompasses everything from eBooks to stock images and even Udemy courses. The idea here is to create a digital good that has value. Why digital? Well, if you’re creating really unique hand-made socks, you can’t just duplicate them and resell them. Furthermore, you have to pack and ship each pair. Both of these things mean that there’s a fixed ratio of labor to income, and we’ve already discussed why that’s not ideal. Digital goods can be duplicated, and we can engineer systems (or use online marketplaces) to deliver them automatically. Awesome.
Depending on how many rental income properties you have and your experience with home improvement, you may be able to do a lot of the maintenance yourself. You likely won’t be able to fix everything but it will be worth it to learn a few common repairs to do yourself. Typically, plumbing and electrical maintenance will cost the most since work is generally restricted to licensed members of the trade unions.

Let’s continue the vintage BMW idea. Old cars obviously require quite a lot of maintenance. Many people will buy a “fixer upper” with the intention of spending their spare time repairing and restoring it. There’s a very obvious market here: a guide to restoring different BMW models. Depending on your knowledge, you could produce detailed guides for the three or four most popular models and sell them. Not everyone restoring a car will buy them, but some probably will.