Usually, keeping a debt/equity ratio of around 30% will result in a maximization of the Weighted avg. cost of capital (WACC); ie, the interest expense is normally lowest when utilizing a hybrid financing structure of 30% debt and 70% equity. Profitability of 20% is optimal because a full loan can be paid off in approx. 5 years; some industries just don’t have this level of net income, but that’s made up in cash flow volume.