It does depend on which university you are attending and what course you are doing in regard to the points and all that.
Uni starts either end of February/beginning of March. That is the start of semester 1, which goes to roughly June. Then there is between 2 or 3 weeks off until the start of semester 2. Please note there is about 1 week off, for Easter during semester 1. Semester 1 is about 12 to 14 weeks long, depending on which uni you attend.
Semester 2 starts mid to late July and goes through to about November. So usually about 15 weeks or so. Again only 1 week off around the middle of the semester. Note that it goes until November due to the exam timetable. So this means there is about 3 months off for summer vacation from the end of one semester, to the beginning of the next.
Some course allow a person to start half-way through the year (that is normally semester 2), everything is just delayed by 1 semester.
If you do a course full time, it is either 3 or 4 years depending on the course. Part-time study takes twice as long. Depending on the course will determin how many subjects you do each semester but usually it is 4 or 5, depending on the credit points.
For example, I am currently doing a Bachelor of Business. All subjects are 12 credit point subjects. I attend 3 hours (some subjects have been 4) at uni for lectures and tutorials, and the difference (in this case 9, is thereotically how many hours outside of uni you need to make sure you get a good mark). However I have heard of friends at another uni where their subjects were only 3 or 4 credit points in total, and it did not correspond to anything about the hours done in a course or week.
My course full-time, would be 48 credit points per semester, but my last degree, where classes were 5 or 10 credit points, was 40/semester.
It really does depend on the university where you wish to go and what the course it. Determine the course, find the unis that offer it, and see what the actual courses have to offer. Usually there will be someone you can email, who can give you some of the information if it is not available online.
One thing you want to note, is that as you will be an overseas student, I believe (AND I might be wrong) you have to pay the education fees (we call them HECS - Higher Education Contribution Scheme) upfront. But I might be wrong about that.