Of course, you can make honst money in Internet info-products, or affiliate marketing, or other such areas where people tend to get drawn to "passive income" fantasies. But, to make real money over the sustainable long-haul, you must treat these like any other business. In other words, you must provide real value to real customers with a real need.
My favorite type of semi-passive income was rental property because it was a tangible asset that provided reliable income. As I grew older, my interest in rental property waned because I no longer had the patience and time to deal with maintenance issues and tenants. Online real estate became more attractive, along with tax-free municipal-bond income once rates started to rise. 

Anthony, nice setup! To your question about the rental mortgages, you haven’t said what interest rate you are paying. As a start, if you are paying more than the risk free rate (Treasury bills) which you probably are, then a true apples to apples comparison would be yes, pay off the mortgage. But, if you are comfortable taking more risk, you have other options to invest in which you *hope* will yield you more over the coming years. You also didn’t say whether the rentals generate net income and if so, how much? What is the implied rate of return on the equity you have invested in them? If you pay the mortgages off, you’ll have even more equity tied up, will the extra net income make that worthwhile? Maybe you should use the money to buy more rentals instead, if purchase opportunities still exist in your town. … this is less of an answer than a framework to analyze the decision, hope it is helpful. 

Hey Alison! thanks for taking the time to check out the post! I specifically outlined the post so it would follow a specific structure. This is so readers know what to expect and it helps with the flow of the piece. I’ve actually just finished up a (shortened) PDF version of the post that includes a bonus idea not mentioned here. I’ll be adding this to the post shortly! You’re right on the ebook suggestion — could easily have been made into one. I noticed that you linked to it from the millionaire blog post, thank you so much. Kimberly and I really appreciate the mention.
If an investor puts $500,000 into a candy store with the agreement that the owners would pay the investor a percentage of earnings, that would be considered passive income as long as the investor does not participate in the operation of the business in any meaningful way other than placing the investment. The IRS states, however, that if the investor did help manage the company with the owners, the investor's income could be seen as active since the investor provided "material participation." 
The only thing better than making money is making money while you sleep. That’s the whole concept behind passive income. You can spend more time with your family and friends, perfect your golf swing or learn another language. The possibilities are endless because you’ve set up passive income streams that provide you a paycheck without needing to clock in. Here are the 10 best passive income ideas that will rock your world.
Who doesn’t like some down and dirty affiliate fees?!  Especially if you realize it can be even easier to make money this way than with an ebook.  After all, you simply need to concentrate on pumping out some content for your own site and getting the traffic in, often via Google or social media.  Unsurprisingly, most people can enjoy their first affiliate sale within 30 days of starting a blog.  Continue reading >
Peer-to-peer lending means loaning money to other people. Specifically, you lend money to people who don’t qualify for traditional financing. Companies like Lending Club and Prosper offer returns in the range of 4-10%, which are a lot higher than a typical saving account. You will be able to select the right investment for you, based on your risk assessment strategy.
Creating passive income is the key to retiring, especially retiring early. If you want to retire early with the stock market you will have to save a huge amount of money, because that money has to last so long and retirement calculators depend on you using your investment to fund your life. With passive income you will have income coming in as long as you own the investment, without every eating away at the principle invested. Creating passive income may take more work than investing in the stock market, but I think it is well worth the extra effort!