Most coaching contracts are guaranteed so the team has to pay after they are fired, unless they get another coaching job. Then the ex-team is off the hook in most cases. This is why so many coaches take a year off and do TV after they get fired. It allows them to collect 2 paychecks, from the old team and from TV.
It gives them the time to wait for a good job instead of the first job that comes along. A guy like Kelly has to decide if he wants to stay in the NFL. If he does, then he may have to take the first NFL job that comes. Because he may not get any other offers.
If Kelly wants to go back to college then he should sit out a year and wait for the job he wants. Texas is probably giving Charlie Strong only 1 more year. Texas is the best job in college by far. They have the deepest pockets and you are in the best recruiting area in the country. You can get any Texas recruit you want and also recruit nationally.
USC hired their interim coach to replace Sarkisian. I don't think they'd fire him this year to bring in Chip but if he has a bad year then i can see them offering Chip the job.
Brian Kelly of Notre Dame has said he wants to go to the NFL someday. He's done a good job at ND so it could happen.