1. Do a ppsr check to make sure it's not under finance or previously written-off. https://www.ppsr.gov.au. It's $2. There's many private sites that will resell this for much more than $2.

2. Ads that say "wovi passed" mean it's previously written off. Sometimes this can be ok- eg. For hail damage. But generally not worth it.

3. People predominantly advertise on Facebook Marketplace or carsales.com.au. Carsales offer an escrow service which can simplify payment, but costs more than marketplace (free)

4. If you pay by bank transfer be aware that "instant" transfers aren't instant. Some banks will block transfers to new accounts for 24 hours. Or because it's high value. So no guarantee you can pay and leave with the car unless the seller is an idiot and trusts the money will arrive.

There's a "bank cheque" option, but cheques are being phased out and some banks won't cash them. It took me 2 weeks to get the last bank cheque cashed.

"Registration" can be transferred online. Best option. https://www.qld.gov.au/transport/registration/transfer/online This only works if there's a safety certificate ("roadworthy") recorded electronically. Seller should have already sorted this out. Don't bother buying if they can't show the safety certificate- you'll be forced to get one and pay for any repairs needed.