A linear income is when you trade your time for money. It’s also known as a work income. The paychecks that you receive are based on the amount of work you do. In this kind of income, you are required to put in hours of work every week. If you stop working, you also stop earning. Hence, linear income requires you to continue working in order to keep earning an income.

One absolute valuation method which may not be so familiar to most, but is widely used by analysts is the residual income method. In this article, we will introduce you to the underlying basics behind the residual income model and how it can be used to place an absolute value on a firm. (The DDM is one of the most foundational of financial theories, but it's only as good as its assumptions. Check out Digging Into The Dividend Discount Model.)
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.