I have read the key to wealth is turning earned income into passive income. What is the best way to do that?

Yes I believe one of the keys to wealth is having mulitiple streams of passive income or at least one strong stream of Passive income. I believe Real Estate in the form of rental properties is a strong form of Passive income, but if we are going to base into internet marketing terms then you could look at website building as the same thing. You can take a website(comparable to a property) and build it up and make it look good and flip it for quick cash or if you have build a nice stream of passive income with this website then you can keep just collecting money every month and hopefully use that money to make more and more money in other various income streams.

So basically take the money your earning with your main job or project and buy another house, website/blog, another job, an investment of any sort and make another stream of income out of it so then without any additional out of pocket money your income is gradually growing.