Hotwire is giving me some crazy rates on car rentals. It is offering me $280 for a week, but only $218 for 8 days. If I buy the 8-day rental, and return the car one day early, what will happen? I don't even know if these are from the same company, so I don't think they can charge me the difference, but is there some kind of penalty for returning the car early? Thanks!