Depends upon the company that owns the aeroplane. Typically you only pay for the flight time, but if you tie the aeroplane up for a whole day they'll insist that you pay for a minimum (typically 3 hours per day for more expensive aeroplanes, 4 hours per day for cheaper ones). Often companies are much more relaxed about it in the week, as the weekend is their main revenue earning time for the aeroplanes.
This is one of the many reasons I like owning a share in an aeroplane, rather than renting. A syndicated owner seldom has a problem taking his/her aeroplane away for a few days and only paying for the flying.
G