Venture Lenders realize startups want to extend runway and pay back as little of principal as possible. Therefore lenders will grant interest only periods, usually the first 6 to 12 months of a loan, where the startup is only paying interest on the loan. This period is usually timed to end right after a fundraise will take place. The logic is the startup will be flush with equity capital after the fundraise and will be in a position to start paying back the loan.