A number of factors affect cost, but you can get a basic idea of how much you will need to spend by working out the square metre area of what you are looking to do and multiplying it by around $1500 – $2000. If you are considering bathroom or kitchen works it is also best to allow additional finds for these items depending on the level of finish and the quality of the fittings you are looking for.
These estimates can not be relied upon as each situation and project is unique. Other factors such as site access, landscaping, decks and other unforeseen expenses will need to be factored in. However a square metre rate estimate will give you a reasonable indication of a initial budget.
Having built my own home on a tight budget on a difficult site, I have some insight into the challenges of keeping to a budget.