Treat it in all respects as if it was an arm's-length transaction between two unrelated parties, and you should be fine.
A loan between two unaffiliated parties would have an underlying business purpose (such as an investment of start-up funds for a new venture); it would bear interest at a commercially reasonable rate, considering all the circumstances and risk factors; the repayment schedule and terms would be commercially reasonable; proper documentation would be drawn up; the arrangement would be documented in the corporate minutes of both borrower and lender.
You should have the same flexibility to custom-tailor the loan terms to craft an arrangement that best fits the particular fact-set involved. Not every loan, for example, is level-payment and 5-year maturity. Just don't stray far from terms you'd reasonably expect to find in a small, private loan transaction to a start-up venture.
Good luck with the new biz.