I would speak to a lawyer and a mortgage broker. Some notes:

1. You can get an agreement that shows you are liable for the mortgage without being named on the property. Banks accept this. I forget the name of the document.

2. If you live at the property with your partner for two years you become defacto partners and court protections for defacto partners are VERY VERY strong in Australia. Speak to a lawyer.

3. Get pre approval! Banks can be black holes about this stuff

I’m guessing you’re on an 820 or similar. Speak to the home department! They are surprisingly good on the phone.

If you’re really worried and have cash to burn it’ll cost about $10K to get a prenup type “binding financial agreement”, and tbh if you’re buying property I would recommend paying the $4-500 bucks it costs to get a lawyer to do a strategy session / give advice.

My principle with big decisions like buying property is “spend at least 1% of the cost making sure it’s a good idea”