If your parents make less than 31500 a year, i beleieve you're entitled to the full rate of youth allowance, provided you're a student. But for every $4 they earn over that threahold, you lose a $1 off the rate of pay. Living at home youth allowance is about half of the away from home rate.
Your parents will be subjected to a income and assets test before any payment is made.
If you can make about 18k whilst also having been out of school for 18 months, then you will be classified as an independent and your parents income ceases to matter.
Michael, you seriously need to think about working whilst at uni, most people do it, and to rely on centrelink benefits alone is unlikely to pay all of your expenses, especially whilst you live at home. Centrelink will not pay you more than $100 a week whilst you are at home. Brendan did offer some good advice, and you must now list your expenses and weigh it against any centrelink payments you might be entitled to. If you don't have an income then buying lunch seems an expense you could do with out. As a student parking/fuel vs public transport would be a no brainer as public transport is clearly much cheaper.
The ulitmate truth is you can't afford to have any expenses if you have no income. Every year at uni you will have to pay for books, materials etc, and your reliance on govt money will not accout for any major finanicial hurdles you may face, ie car repairs and/or special events.
Even with centrelink assistance, i'd advise you begin work too, as the home rate of pay for youth allowance would not allow much freedom in your activities and i'd be suprised if it covered all of your expenses