There are ton's of co-working spaces but they are expensive and have long contracts generaly speaking so you can work at the librarys which were great, quiet, aircon etc.
Electron Workshop is a nice coworking space which also has per day membership. Coffee is included in it and bicycle parking available too. along with tables they rent private office. The internet is quiet speedy up to 70mbps.
Melbourne Airport- Optus store provides sim card, its located outside the arrival gate near international baggage counter. you can choose a plan as per your wish.
the best spot for startup enterpreneurs.engaging and wholly useful. wish it was closer to home.coworking space very close the Richmond station.great co-working space friendly staff.