For example, if a business has $150,000 of net profit and $350,000 of total revenue, the net profit margin would be $150,000 divided by $350,000 multiplied by 100, or 42.857 percent

This I understand, what I am unsure is if Net profit means the same thing as operating.

what I also am unclear of, is how they calulate total revenue versus net profit and how this relates to net investment return.

Consider that in month A they generate 8% net profit off a million in revenue. They take all the money in fees and then pay 92% back out. Their actual investment is nil but they make $80,000. If we assume their net investment at risk is only $100,000 in capital expense and the rest is paid as they go from monthly payments, full return on investment would be 80% a month. Since they probably have reserves calculated into their expense model, what I want to know is what is their yearly return on capital at risk. Since they probably have no personal guaranties, then the capital is the only risk. If they are leasing the facilities and equipment, the actual capital expenses could be quite low making the return on investment huge.