ahh theres a few options for you, have a search around on the general med forum.
basically if you really want to live in on-campus accommodation you're looking at forking out exorbitant amounts of money for substandard quality. the only reason i can possibly imagine you'd want to stay there is to experience the social aspects of uni life, which i totally respect if that's what you're looking for.
I had a few friends at Mannix and Halls in first year and some of the stories I've heard 0_o (probably more so for Mannix COllege).
If you're really set on experiencing college life then I say go for Mannix since there's more meddies there and it's much closer to the uni (the part where you'll be studying in).
Another option is you could look for share accommodation in Clayton and surrounding suburbs, that'll be way cheaper and a better environment for studying. It sucks for you since you don't have access to Monash marketplace (where they advertise rooms in share houses) but you can go to monash.edu.au/study/accommodation if you want to have a look at some places.
All the best and if u have any questions don't hesitate to ask.