Rentals, just like stocks, throw off cash. With rentals we call that cash “rent”, and with stocks we call it dividends. A significant difference however is that the S&P 500 has appreciated at ~6% per year (above inflation) for the last 100 years…..Real Estate has had almost 0 growth above inflation. So are rents higher than dividends? Maybe, maybe not. But unless you got one heck of a deal, the delta in rent over dividends will have a very tough time making up for the 6% per year difference in appreciation.
In 2017, AirBnB purchased luxury vacation rental provider, Luxury Retreats, and other consolidations in the marketplace have happened with leading sites like InvitedHome's acquisition of PPG rentals and Seasoned Dreams' platforms, and Expedia's $3.9 billion acquisition of another vacation rental giant, HomeAway. The market is booming and the time is ripe for entry, no matter how big or small your home or condo might be. 
One of the things I'm surprised your article doesn't mention is the tax advantages of this type of investment. The depreciation and rehab costs (purchasing distressed properties) can be huge deductions to ones income taxes, which none of the others have. Then, along with the appreciation of real estate, this passive income investment outperforms the notion of maxing out my 401k as well.
What’s the catch? None, really. Cash back apps act as affiliates for many online merchants, which means that whenever you make a purchase through one of the apps, they get a small commission — but then, they give you a portion of that commission as “cash back”. For example, if I buy a pair of Nike shoes through the Ebates app (or website) and spend $75, Ebates may get a $10 commission but then they’ll pass $7 back to me. It’s basically a way to get sale prices on stuff that isn’t on sale!