Affiliate marketing is a great way to earn passive income. You can find products to share via your social media platforms, website, or through an email blast. Once somebody purchases a product, you are given a 20-70% commission. I like to use Clickbank and find affiliates that correspond with my meditation brand. You can also seek affiliates out directly such as Hay House which offers a 50% commission on any courses sold.
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.