(AUS) Buying an investment property when you don't even own a house yet? Crazy?

Hey r/personalfinance,

I have a rather unusual(i think) query about buying an investment property. My parents have inherited a house(valued at 750K -850K) in Sydney , which they have no plans to sell, as they're quite content living where they do. They both receive pensions, so renting out that house is out of the question, as it would nullify their allowance. They've said that I can live in the inherited house rent free as long as I pay the rates, and other associated costs of running the house. So, I essentially have a place to stay at indefinitely, which is rent free. However, The house does need repairs, so I won't be moving there for another year of so.

I've started to think about what possibilities this new arrangement could offer me. At the moment, I live very close to a very internationally popular university and the rental market here is always booming. We have new international students flying in every year and scooping up every piece of rental real estate within a 15km radius of the university. There's also a lot of new development in the area, with a new half a billion dollar mall renovation and a very popular business park with many multinational corporations calling it their home. As such, residential space in this area is quite limited, and in very high demand.

This brings me to my actual question (thanks for reading this far). I'd like to buy an apartment in this area, and rent it out to pay off my mortgage on it. The price of the apartment in question will likely be close to the $1mln mark. My plan is to ask my parents to finance the down payment on the apartment, by taking out an equity line of credit on their inherited house ($200,000), which I will pay off while living in the inherited house. While my tenant on the investment apartment pays off my mortgage on that property.

I make 60K per year and my partner will be graduating soon and starting off at 64K. Our cost of living will be quite low as we won't have to pay rent, but will have to pay off the $200,000 line of credit, and also any time on the investment property where we would not have a tenant. I'm very confident in that rental market, and being directly adjacent to the university and mall, i think that the chance of this happening would be very unlikely, however, I believe our cash flow is enough to float both payments for a short while.

I've had a thorough think about this plan, and to me it looks quite good. That being said, I really know next to nothing about real estate investment and I could be quite wrong. What do you guys/girls think?

Thanks in advance.