If you are first time buyer and/or buying a house as a primary residence you might be eligible for a concession on the stamp duty. Generally, if you're a foreign resident then you need to pay extra 8%.
It's really simple. Office of State Revenue has a stamp duty calculator that you can use. Simply follow the link: https://www.apps08.osr.nsw.gov.au/erevenue/calculators/fhba.php