You will be able to buy a permit for Semester 2 only at half the normal rate (so you'd be paying $185 or so). That being said, the half year permits are issued only on an availability basis - generally speaking there will be some available.
Parking at Uni (in 'student' blue permit zones) is free only during the holidays and the exam period. Parking during the semester is not free.
If you have a friend that lives near to you, consider carpooling. It makes the journey less boring, it's better for the environment, you save money from (presumably) halving your driving cost and from not having to buy a permit (they give free car parking for carpoolers) and you park closer to campus. They only issue is that you might have to go to uni at earlier times than usual or leave later - but you can use this time to study or just sleep! It's a win-win-win-minor loss in my opinion!