Before you start a building project it's useful to have some idea of your budget and to help with that, it's really essential to have a rough idea of building costs. Just as long you remember that building costs are only as accurate as the detail you are able to put in to them.
To give a very broad indication, $1500 m2 is very cheap, $2-2500 m2 is more commonplace while figures from $3000 m2 and upwards are typically more consistent with complex builds such as architecturally designed houses.
Having said that, all building projects are very different and the best way to get an idea of the cost is to talk with your builder and designer about the design and different materials you want to use from cladding and joinery to the appliances, and get their ballpark figures.
When you get your quotes, check that you’re comparing apples with apples. Cheaper quotes may have left out items or deliberately under quoted. You could find you pay more down the track. And don't forget to include a contingency of approximately 10% in your budget. Unexpected extra costs will almost certainly crop up.
When you're ready, using a Quantity Surveyor to price your project is a good way to way to get the most accurate estimate of your building costs. Early on is the best time to understand the expenses you'll be in for, while you're still able to tweak the plans. The further down the track you are when you change your mind, the more serious the effects on the budget!