It can be very expensive parking your car at the airport when you are away on a trip but a Bay Area Start-Up launched a few months ago is trying to cut those prices down to size. You drop off your car, they clean it and then hand you a check. There is a catch, of course; you have to be willing to let a complete stranger drive your car while you’re gone. They first started in San Fransisco, now also in Boston, they make money by renting out ordinary people’s cars for half the price of Hertz or Avis and business has been huge for FlightCar. Renters get to pick what they drive and FlightCar’s job is to make every car rent-able, even the messy ones. You get paid based on how new your car is, and how much it’s driven and then upon return, your car’s all clean and they have a $30-$40 check waiting for you and Even if nobody rents it, the parking and the car wash are still free. FlightCar is growing and hopefully will expand in other cities.