Dual occupancy - upstairs/downstairs

Does anyone know of a project home builder in Sydney who has a multi-family design where there's a main entry door that goes into a foyer, with stairs leading to a door to an "upstairs" home and another door leading towards a "downstairs" home? Each floor would have 3 bedrooms, 1 living area, 1 kitchen and 1 dining area. The dividing doors could then be left open so that it combines as one single 6 bedroom home.

I would think this would come under a class 2 building not a class 1 (google building clarifications Australia) if you have a foyer with 2 seperate entry points. I know in WA the local governments look at these rigorously and more than likely would have to be done as an apartment/unit. I would ring your local council first just to make sure you can do it as a residential building (class 1) as you wouldn't want to pay the additional price if they deem it apartments or units.
Sorry don't know about builders in Sydney but don't go with anyone who hasn't done this type of house before