Expansion capital comes in only two forms, debt and equity. Debt capital is appealing because it is cheaper and likely easier to obtain than equity. The degree of debt financing used can be described using the concept of leverage (Debt/Equity Ratio).
A useful approach to discussing the effects of debt choices on an operation is through the standard return on investment calculations. The profits of a business represent a rate of return to the capital invested in that business. The return to total invested capital is usually described as the Return on Assets (ROA). This is what the business entity earns. We are often concerned with what the owners of the business earn. Typically there are two "owners" namely the holders of the debt and equity capital which make up the financing package. The returns to the business entity are shared between these owners. As a rule the debt holders get paid first which means equity holders are residual claimants to any profits. As such, the equity owners absorb all of the variability in earnings.