When you create residual income, you are taking a step towards making extra money in a manner that does not require constant effort. The stream of income is actually generated from something specific; a specific effort that you put forth to create the stream of income opportunity in the first place. Residual income is not always a passive manner of making money.
Residual income valuation (RIV; also, residual income model and residual income method, RIM) is an approach to equity valuation that formally accounts for the cost of equity capital. Here, "residual" means in excess of any opportunity costs measured relative to the book value of shareholders' equity; residual income (RI) is then the income generated by a firm after accounting for the true cost of capital. The approach is largely analogous to the EVA/MVA based approach, with similar logic and advantages. Residual Income valuation has its origins in Edwards & Bell (1961), Peasnell (1982), and Ohlson (1995).