i guess it can be done if you are living on shared basis with colleagues/friends. I have heard horror stories of international students living in outer western suburbs of melbourne sharing upto 4 students in a single room..

Reasonable lifestyle is very relative term...what is reasonable for you might be dog's life for average aussie..

You can get a backpackers for $20 per night in Central Sydney (Kings Cross) - which would also cut your travel costs (and street entertainment is free). Maybe an option for when you first arrive and are looking for a room/flat to rent?

Good luck!