Cost of house extension in Sydney

Hi,

Can someone advise what would be the general cost of house extension in Sydney? I need shell only – walls, roof, windows and doors.
I’m considering one or two levels extension.

And also how much would I expect for building a garage?

I‘m looking for something really simple in shape.
– If it’s two levels it will have kitchen on the ground level and bedroom & bathroom above.
– If it’s one level – it will simply have the kitchen / bathroom on the ground level.

I wonder what the general guide for the price cost for building a shell only (I’ll budget the fittings separately).

Thanks