this is where having an MBA (or undergrad business degree) can be helpful. note, i'm not saying you need a business degree to be a founder, just that it can help if you already have it. =)
in business school, you learn that much of finance & accounting is storytelling with numbers, but with the added twist that there are legal consequences for crossing over (and sometimes, just into) the gray area. that's what sam is pointing out, where the gray area ends and the legal consequences start.
as others have pointed out, quantitative finance & accounting classes can be very helpful:
* financial accounting
* managerial accounting
* financial markets
* investment finance
* corporate valuation
* entrepreneurial finance