Check old threads but basically 98% of people live off campus. The on campus housing are the "colleges" which a few people will live in (International House), but there are cheaper options. Most of the stuff first year is in St. Lucia, but there isn't a whole lot going on there in terms of shops/nightlife/things to do. There's a supermarket, a Thai place, a bottle shop and a few other shops but most people live elsewhere. Second year you will have to spend a bit more time in the hospital (RBWH, PAH, or Mater) and they're all on the 66 bus route.
For that reason, a lot of people live somewhere along or adjacent to the 66 route, e.g. West End, South Brisbane, CBD, Woolloongabba, Highgate Hill, etc. Some people will live in Toowong, Auchenflower, Indooroopilly, etc. If you want to live on your own, depending on your financial situation, you may have to live a bit further out for cheaper rent. I think the rental market is favorable for renters right now because they've been building like crazy that there are a lot of vacant units. For a 1BR in a central location though, I'd expect to probably pay upward of $400 (probably like $425-450 AUD) per week.