I'm still in the process of experimenting with my method to see how far I can take it, but the basics of it work already.
A lot of what people define as "passive income" is questionable. Most, if not all, passive income investment strategies require you to hold down a job, or other income, while financing assets that some day, HOPEFULLY, will be paid off enough that you don't have to work ever again.
Most of those plans take too long for my satisfaction. There are other means and methods if you learn and apply yourself. My book will hopefully detail and compare my method with a majority of others.
The obvious ones to look at, if you can invest time and/or money -
* Share trading * Property investment * Property flipping/options * Google AdSense (or similar) * Affiliate marketing * Tim Ferriss' muse / 4HWW * Network marketing/MLM * Website flipping
All of them have varying degrees of learning curve and time commitment to make happen. Few people will tell you how much commitment you need to make, they just focus on dangling the carrot.