Airlines normally hire you as a fulltime employee. I have known pilots who have taken periods of unpaid leave so they can go and do other things (such as fly warbirds on the European airshow circuit
), but this is not always a good prospect for the airline, it may cost them more money to get you current again when you come back.
P.S. Your airline should carry "loss of licence" insurance for you so if you lose your Class 1 you have the money available to allow you time to change careers.