This can be a little easier said than done, but if you have a large social media following, you can definitely earn money promoting a product or advertising for a company. You can even combine this with different marketing campaigns if you are an influencer and have your own blog (advertisement + affiliate income). This is how many bloggers make money! Again, it is not 100% passive but once set up correctly and then scaled, can be surprisingly lucrative.

There are three main categories of income: active income, passive income and portfolio income. Passive income has been a relatively loosely used term in recent years. Colloquially, it’s been used to define money being earned regularly with little or no effort on the part of the person receiving it. Popular types of passive income include real estate, peer-to-peer (P2P) lending and dividend stocks. Proponents of earning passive income tend to be boosters of a work-from-home and be-your-own-boss professional lifestyle. The type of earnings people usually associate with this are gains on stocks, interest, retirement pay, lottery winnings, online work and capital gains. 

The paper identifies, and then resolves, a number of seeming puzzles in a newly identified set of stylized facts entailing movements in factor returns and shares and the wealth-income ratio. Standard data on savings cannot be reconciled with the increase in the wealth-income ratio: there is a wealth residual. An important component of this is associated with rents: land rents, exploitation rents, and returns on intellectual property.
I wouldn't think of a high yield savings account as a source of passive income but your savings should be getting something (less like Seinfeld syndication residuals and more like a commercial jingle residuals!). It won't make you rich but it's nice if your baseline, risk-free rate of return on cash is 1% or more. The best high yield savings accounts (or money market accounts) offer higher interest rate and there is absolutely no risk. CIT Bank currently leads the pack with the highest interest rate.

In order to generate $10,000 in Net Operating Profit After Tax (NOPAT) through a rental property, you must own a $50,000 property with an unheard of 20% net rental yield, a $100,000 property with a rare 10% net rental yield, or a more realistic $200,000 property with a 5% net rental yield. When I say net rental yield, I’m talking about rental income minus all expenses, including a mortgage, operating expenses, insurance, and property taxes.

You can also establish passive income through blogging. JP Livingston, who retired early at age 28 with a nest egg of more than $2 million, earned more than $60,000 in one year from her blog. With the use of affiliate commissions and online advertisements, a good portion of these earnings were passive income — she spent less than five hours a week blogging.
It shouldn’t come as a surprise, but people who regularly monitor their finances end up wealthier than those who don’t. When you were a kid, keeping track of all of your money in a porcelain piggy bank was pretty easy. As we get older, though, our money becomes spread out across things like car payments, mortgages, retirement funds, taxes, and other investments and debts. All of these things make keeping track of our money a lot more complicated.
7. Royalties: the creation of music, books, inventions, machines, patents. A royalty is something you have sold or created and put it on a platform that you do not run and then receive compensation based on when the item is purchased or used. Most of us do not have the potential to quickly create royalty streams. Not to say you couldn’t specialize in something and write an ebook or if you are musically inclined you couldn’t write a song, but to create true residual income, that is going to take a lot of effort and skill. This is the purest form of passive residual income, if you can achieve it.

Residual income is money that is earned on a recurring basis, typically as the result of a single original action. Rather than earning an hourly wage, residual income is typically generated through an initial investment of time or money with the goal of earning continuous payments. Once the initial investment, product, or service is made, the ongoing income that is earned is generally passive in nature.