transport is quite costly with the metcard, not too sure about the current rates but you should check the met website.

one room apartment im not too sure, but i can tell you a 2 room apartment costs ~AUD$1k a month (my friend was living @ lt. bourke st.). i would suggest you share with someone. and advisable to stay near uni so you save on transportation, walk to uni. with a homestay i guess you won't get as much freedom. or maybe you can consider the dorms if unimelb has any

food, can honestly tell you supermarket there and here around the same price, just different currency.