Be cautious with PM offers from non-locals. I know you are looking for sellers based in Australia but it's always healthy advice to stay alert and careful at all times. There are some non-local scammers who can be very creative and will improvise devious ways to make a quick buck.

If they realize you strictly operate locally, they might find naive locals to act as a conduit for receiving your 40k AUD. It's the classic MITM scam. Be wary of deals that sound too good to be true or when a trade starts getting complicated ("I can't do it, travelling overseas so I suggest my brother or cousin in Broome or Port Hedland deals with you.."). You will notice that they will suggest places that are geographically remote which is intentional to avoid meeting up. To spice things up, they will sweeten the deal by countering your preev + 2.5% offer with much more tempting terms.

With local offers, stay safe. People have been known to meet up and were later assaulted and robbed.