That income is considered residual income because as long as the apartment is rented and the rent is collected, the income is earned without additional effort. The effort came when the property was purchased and a tenant was found. Each month after that, the money automatically is paid without buying the apartment again or finding the same tenant each month.
Many bloggers and social media influencers build significant residual income through affiliate partnerships. If a blogger promotes or mentions a product on their site, and readers purchase the product through the link provided, the blogger earns a percentage of the revenue. The same goes for social media influencers. If someone promotes a product on Instagram and their followers purchase it through their link, the Instagrammer would receive a portion of that revenue.

This world is a dangerous place to live, not because of the good people that often act in irrational and/or criminally wrongdoing ways within the confines of their individual minds, core or enterprise groups, but because of the good people that don’t do anything about it (like reveal the truth through education like Financial Samauri is doing!). Albert Einstein and Art Kleiner’s “Who Really Matters.”
If you're looking to get started in real estate, look at a crowd funding solution like RealtyMogul. It works similar to LendingClub - you commit as little as $5,000 towards a property. When the property is fully funded, you become an owner, and will receive your share of the earnings and appreciation in the property.  Check out RealtyMogul to learn more.