Question normal

How demanding are the contracts or terms of the locum tenens for most physicians? I ask because I hope I could use this as a way to work some more hours and pay back my loans in the future a little more quickly. Is there a minimum # of hours you have to work at a time?
By "privately", I mean are you able to contract out independently, or do you have to join an organization? Similar to how ER doctors are contracted through a group to a hospital...