build and sell OR sell land

Own a 809m2 subdivided land (Corinda, Brisbane) with an old house rented currently.. My dilemma is whether to, sell the house and land as is or

- get rid of the old house
- building 2 new 2 storey house and sell
- quote/house $300k

Question

- what is demolition cost ( house is most likely asbestos build )
- what is the cost of ID servey
- cost for providing services to both the properties

The above 3 components are not included in the 300k build cost

Does anyone have any contacts for good demolition company in Brisbane?

much appreciated

build and sell OR sell land