Those who choose to focus on passive income will need either family money, funds from investors, or the nerve to borrow large sums by taking on debt to fund the purchase of assets. Consider someone who takes out substantial bank loans to build an apartment building or buy rental houses. Although this can turn a very small amount of equity into a large cash flow stream, it is not without risk. When using borrowed money, the margin of safety is much smaller because you can’t absorb the same degree of setback before defaulting and finding your balance sheet obliterated.

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.