Hi Carla,
Welcome to the forum.
Firstly check out the please read sticky at the top of the forum. It has links to the visa / immigration site (and other useful sites) since you need to know you can get in. Do you want to move permanently? Some visas are temporary and others permanent.
Sydney is lovely and expensive too. If you check out some recent posts a member has said which areas they prefer in Sydney.
I don't know Sydney that well so can't recommend a college.
We're in South East South Australia (2 adults) and these are our costs per month:
Food - A$550
Electricity - A$70
Gas - A$65
Water - $62 (if renting this may be paid by the landlord)
Property websites:
www.domain.com.au
Real Estate, Property, Land and Homes for Sale, lease and rent - realestate.com.au
Hope that helps,
Karen