The third most common is real estate investment. To many people, this is their appreciation on their home, although some tend to think of this as a pseudo-investment as the loan interest you pay - minus the tax deduction isn't really a net gain - it's just better than renting (assuming the market goes up.) For example, if you bought a $200,000 home on a 30 year mortgage at 5%, your total expenditure is +$386,500, plus maintenance, property tax, etc. Your tax deduction would yeild about .30 for every $1 of interest paid or about $55,000. So if you sold that home for more than $330,000 after 30 years, you got your money back. If not, you would at least get some money back, but it still far from a "guaranteed" investment that many people thought it was before 2008.
Building a website still remains a viable way of earning passive income online despite it being such a competitive venture. Since the internet is saturated with blogs, an entertaining website featuring quizzes or games is a good alternate. Such websites are not too difficult to make and they are easy to promote on social media. They can attract visitors, who will spend a significant amount of time on the site, in droves. Once a site starts recording several thousand visits each day, use the Google AdSense system to start earning revenue through advertising while you relax.
Affiliate Marketing – Affiliate marketing is the practice of partnering with a company (becoming their affiliate) to receive a commission on a product. This method of generating income works the best for those with blogs and websites. Even then, it takes a long time to build up before it becomes passive. If you want to get started with affiliate marketing check out this great list of affiliate marketing programs.