The Victorian rule, as it applies here
Consumer Affairs Victoria calls an RWC a general safety check, done by a licensed vehicle tester. It's needed to sell a registered vehicle, to re-register one and to clear some defect notices, and it lasts 30 days from the day it's issued.
Mildura sits on flat land and spreads a long way: Deakin Avenue alone runs 12.1 km and is known as the longest straight avenue in Australia. Use the postcode where the car actually is, whether that's Irymple, Red Cliffs, Merbein or Nichols Point, so the tester isn't on the other side of town.
What Mildura sellers run into
A buyer from the NSW side
Buronga and Gol Gol are a short drive over the river but they're in New South Wales. A car brought in from another state needs an authorised unregistered vehicle inspection there, the blue slip, which NSW makes valid for 42 days. That part is the buyer's, but it helps to tell them before you shake hands.
Buyers from Adelaide or Melbourne
Adelaide is 399 km away and Melbourne 545 km. A buyer taking the car to South Australia is under that state's rules, so they should check with its transport department before they collect.
Summer heat
Some summer days pass 40 degrees here and the record is 48.6. RACV says hot weather weakens battery performance, so a car that starts slowly on a hot afternoon needs a battery test before it goes up for sale. Check the tyres for sun cracking while you're at it.
Block utes
Mildura is ringed by irrigated horticulture, from citrus to wine grapes. A ute that has spent its working life running between rows is worth having a mechanic check for steering and suspension wear before the RWC.
If it were our car
We'd have the battery and tyres looked at before summer, fix anything we already knew about, and get the RWC the week the car is listed. If the likely buyer lived on the NSW side, we'd mention early that their own state's inspection comes after ours.