Going against the normal Industry practice I am going to list some figures for budget purposes which, as frightening as they may be, will give a fairly good indication of what you might be wanting to make allowance for. (Typical Newcastle Hunter Area)
Generally if someone asks for a "budget" I'd advise somewhere between $600 - $800/m2 (for supply installation and concrete)but this may vary significantly depending on numerous outside factors. Costs will vary depending on what needs to be done if you need to meet compliance, every site is different, every council is different. There may be additional, sneaky costs which may not be immediately obvious such as:
Bushfire, Mine Subsidence, Flood, Acid Sulfate Soils, Survey, Geotechnical reports or Arborist reports. Each of these, if they are required will add costs of anywhere from a few hundred to a couple of thousand dollars EACH
Before you start building, compliance type may need to be determined. It may fall into, Exempt,
Complying development, (either through council or private certifier) or require a DA (development application)
DA around $500
Complying Development or Construction Certificate between 1000- $2000
If the project value is above $20,000 Home Owner Waranty / HBCF Insurance is a mandatory requirement Allow around $1000
Drafting and council or certifier submissions allow $1500
Site work is a bit difficult to determine $???
Demolition / asbestos removal and waste disposal $???
Concrete allow around $120 -$150/m2 assuming a fairly level site with good access.
Construction again varies starting from around $90/m2 upwards depending on design, size and accessories
Then you have the kit price.