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 term “residual income” refers to the income that someone makes after their work has already been completed. An example of residual income is the earnings an author continues to make on a book after it has been published, when fans continue to purchase copies years later. Residual income is ideal because it is money that is being earned while doing nothing in the present moment to earn that money.
Owning property can earn you passive income for decades to come. Once you purchase a duplex, home, or apartment building as a rental property, you’ll earn a consistent monthly income with little work. Rent should cover your mortgage, taxes, repairs, and other expenses. You’ll continue to earn income by paying off your mortgage with the rent money and saving excess rental income.
Throughout his teaching, Shea will help you master the skills necessary to build an Amazon affiliate store that functions just like a powerful e-commerce site. That includes picking a niche and doing relevant keyword research; picking a theme for your affiliate store; setting up that store; implementing e-commerce SEO best practices, promoting your site; utilizing basic email marketing; maximizing conversions; and eventually outsourcing your work to efficient virtual assistants.

I agree mostly with the real estate advice. I’m looking for ways to take advantage of the condo I own to get up the rent from ~$0.90/ft to the $1.2-1.5/ft that seems more like the range in the same area. I’d have to put in a bit of capital (probably 10k on the low end for just the basics up to 40k if I wanted to remodel the kitchen and 2 bathrooms up to par with the area), so the return is likely there if those upgrades warrant $1.30/ft (given the unit is larger than most 2br/2ba in the area).

Residual income is calculated as net income less a charge for the cost of capital. The charge is known as the equity charge and is calculated as the value of equity capital multiplied by the cost of equity or the required rate of return on equity. Given the opportunity cost of equity, a company can have positive net income but negative residual income.