Building cost and builder in Melbourne

custom probably not. Volume, most defiantly, but spec would vary. If youre doing a knock down, there additional costs associated with that that will eat into your budget vs a greenfields build just be aware.

As to recommendations for volume, just take a look at builder designs online and start short listing. Then I would suggest you take a look for any unhappy customer facebook groups of builders you are considering in your due diligence. That should help you weed out some well known builders with huge marketing budgets but less interest in doing things right. When you settle on some designs you like, go to their displays and ask the sales people for a price list for the "as displayed" options. That will give you a view to how much more what you're looking at costs VS the advertised base price.

and for gods sake, make sure you budget a couple grand for all stage independant inspections. Dont trust the builders "inspectors" or surveyors to do right by you.