For car prices, check out www.carsales.com.au
For car insurance, check out www.nrma.com.au
For rental places, check out www.realestate.com.au
I'm a bit biased towards Sydney because I live here and there are many great aspects of it, however it is more expensive than the other two as previously mentioned.
What's your budget for rent? $250 on rent and a $100k car :P?
If you want a nice one bedder in Sydney close to the CBD (CBD = Downtown) I reckon you're looking at $400-500 a week in rent...