The TAJ team that runs a Mustang GT is occasionally looking for a driver. I know LD raced with a team that has 2 Paseos? sp. I dont know if they are looking for drivers.

The cost per event is about 800 to $1000 per driver. Our last race was $250 in entry fees and licenses, then about $600 in consumables. But thats including the hotel, Fuel for tow vehicle etc..
We usually driving a 2 hour stint each day.. so 2 days. or Sebring will be 2 hour drive then 6 hours off then another 2 hour drive. And 2 or 3 of the drivers will also be able to do Night racing.. Something that is a different experience.
Most of the teams have a well established base of drivers they use - rotate. Depending on schedules and funds.