The best thing you can do, if you want to investigate a location legally, is to go to your local city hall or local police station and ask for permission. Get it in writing so that when you do investigate then you can present the written consent to the authorities should they happen to stop by and ask what you are doing there.
What does NSW stand for exactly? Have you tried looking up various haunted locations in your area on the internet?
To get permission from city hall, you go to city hall and ask who owns the property you are wanting to investigate. Then you contact the proper person and type out a permission paper and have the person who owns the property sign the bottom of it and giving you permission. If you can't find out who owns it, then contact the authorities and have them sign the paper making sure that you put in the paper that you will not be causing havoc, or touch anything that doesn't belong to you etc. Hope this helps