Hi a friend suggested I try this. I met my partner in early…

Hi a friend suggested I try this.
I met my partner in early 2007 when I moved to Australia from NZ and during this time when I worked part time in parliament - I also worked for him and was given cash sums as payment. In 2008 we moved in together, I moved to his home city where he was the main provider of income for me and I still continue to do work for him. In early 2009 we purchased a million dollar home together - with both our names on the agreement as joint owners. I did not contribute any money towards the deposit and ontop of that my partner had agreed to invest a lump sum of money into the home to ensure it was debt free and give me a level of security as I had finished my work to assist him and he was my sole source of income provider in my assisting of him. When it came time to sign the agreements - my partner then decided that it made better financial sense to take out a mortgage to the full amount on the property because the interest paid in doing that was a lot less than the interest he was paying on an individual overdraft he had taken out before meeting me and subsequently paid that off. I agreed because it made financial sense to do that but I am now wondering where this leaves me if the relationship was to demise? We now have a very large mortgage - over $850,000.00 and my name is XXXXX XXXXX agreement as joint owner of the home with that large mortgage. He told me that I was entitled as his defacto partner to make claim on his assests if I was to leave anyway but I am not sure how that will go in a court of law if it came to a point where we parted our ways as I haven't contributed anything finanically, though have worked for him saving him alot of money in the process..
Can you let me know what my likely position is regarding the law, my responsibility to the mortgage and also what I can claim as his defacto (we are actually engaged to marry).