All I know is parking around Brisbane hospitals is expensive. Far better to catch a taxi in and out.
In terms of accommodation, if you directly approach owners of b&b's or motels, they may be able to offer you a reduced accommodation fee. Ringing around real estate agents, you might be lucky enough to score something there which is suitable to your needs too. Not every service is openly advertised.
Thinking outside the box, does the treatment have to be in Brisbane? Hervey Bay has a great breast cancer treatment team and you could stay at my place on the beach at Burrum Heads. No trouble to run you in and out. Spare room here doing nothing.