SIM card vs. rental phone?

If I can secure a GSM phone at home (in the US) before I travel to
Australia, what costs will I incur in order to have it working for me
while I'm there? Besides the SIM card, do I need a contract? How
much is a SIM card (and whatever else I need)? Thanks for your help!

Mboethi1@m (MattB) wrote in message news:<faf2387e.0307101944.7eccf86c@ com>...
> If I can secure a GSM phone at home (in the US) before I travel to
> Australia, what costs will I incur in order to have it working for me
> while I'm there? Besides the SIM card, do I need a contract? How
> much is a SIM card (and whatever else I need)? Thanks for your help!

I see that Optus seems to have the best national coverage (Australia).
Do they sell Sim Cards? Where in Sydney and Melbourne can I get one
from them?