Thankfully it's easy to get good well priced short term accom in Cairns. Look for a commercially run sharehouse. You'll get your own room (lockable) in a quiet property and most places throw in some free meals etc...You can pretty much walk in with your bags and it's all done. Will set you back between $120 - $150pw. If you are going up between March and Oct though book as far in advance as you can as it's peak season and places will be packed.