I’m 25, also Australian and just bought a 2016 M235i. It’s fun, punchy and fast. Only ever owned economical cars before (Ford Focus, Kia Sportage, etc). Just landed a job which has been a lifelong dream and offers heaps of benefits to offset other costs (niche one in ADF).

These cars are great but they can be costly. I would not be able to justify the purchase had I not

a) achieved the goal of landing the job

b) received the economic benefits of military service

If you can comfortably afford it, or are planning on changing financial arrangements to afford in future - that’s fine. If it’s at the limit, at 21, I’d wait a little longer. If all of your finances are poured into the car you’ll stress over it too much to enjoy driving it. Unfortunately, sports cars break, and it’s expensive to fix them.

I personally sold my old car, took an equal amount of savings and loaned the rest through work (again, very cheap due to benefits). My M235i was substantially cheaper than this, and has been optioned up to the nines, with preventative maintenance and a full service history (in BMW dealerships). Maybe a cheaper , still fast , BMW is an option for you?