Demolish and rebuild on slight sloping corner block in Brisb

Hi all

I'm new to this and would love your advice.

We have a post-war in Seven Hills on a lovely corner block (600sqm) that's pretty small and we need more space. Raising an option but to get rid of the asbestos internally and raise is SO expensive.

So we are thinking that for a bit more we should demolish and start new.

So here are my questions:
- does anyone know if there is flexibility in the setback from the corner? It's a big space we have to leave clear and restricts where we can build.
- equally has anyone had the setback from the front relaxed (so it's 4m instead of 6m?)
- which spec builders will build on a slope that might require a little digging out and some minor retaining walls (750cm dig out). Clarendon already said they would be unlikely to help us.

We need to stick to a budget of $400k for the demo, move out and rebuild and we can't build bottom of the range (because we don't want to!) and the area is really good so long term we need to make sure there is a nice house on the block.

I guess we could also build split level (double storey) if digging out is really expensive?

Right, would love any and all advice as we are first time builders!

Thanks!