Passive income is attractive because it frees up your time so you can focus on the things you actually enjoy. If a doctor wants to earn the same amount of money and enjoy the same lifestyle year after year, they must continue to work the same number of hours at the same pay rate—or more, to keep up with inflation. Although such a career can provide a very comfortable lifestyle, it requires far too much sacrifice unless you truly enjoy the daily grind of your chosen profession. Additionally, once you decide to retire, or find yourself unable to work any longer, your income will cease to exist unless you have some form of passive income.
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.