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.
The primary philosophy behind the residual income model is that the portion of a stock's price that is above or below book value is attributable to the expertise of the company's management. Accordingly, it becomes a handy tool for calculating what the "real" value of a stock is. It is important to note, however, that analysts should pay special attention to incorporating changes in book value per share caused by share buybacks and other unusual events that may distort the analysis.
In equity valuation, residual income represents an economic earnings stream and valuation method for estimating the intrinsic value of a company's common stock. The residual income valuation model values a company as the sum of book value and the present value of expected future residual income. Residual income attempts to measure economic profit, which is the profit remaining after the deduction of opportunity costs for all sources of capital.