Welcome Alex.
Your timing is pretty good. There's a rally on this weekend, and they still need a few more people for officialling roles. If you're available, get in contact with Tamsey or Mark on here and see what they can arrange for you as an intro to the sport. They may put you in contact with someone else (probably the officials coordinator), but I can't remember who that person is at the moment.
Rob and Russell (among others) are also organising quite a few khanacross events this year at Symonston. They are a cheap way of getting into motorsport and having some fun on the dirt (or mud, depending on the weather). Your first event there is likely to set you back a bit over $100 (club membership, license and entry fee). A standard road car is fine as long as it's mechanically OK. You'll need a fire extinguisher mounted in the car, as well as a helmet. Helmet/extinguisher could be borrowed if you get desperate. From there, each khanacross will set you back about $50-60 for entry fee.
If you're willing to travel, there are also some other events run by SKDAC near nowra, as well as a few events around Sydney/Wagga/Central Coast etc.
Helping out at local rallies is a great way to learn about the sport. It also helps to build a long list of rally friends to help you out if/when you decide to take the plunge and buy a rally car.
You could also try your hand at navigating/co-driving as a step into rallying. Either driving or navigating will require a license upgrade from khanacross type events, but once you take that step, you'll never look back.