If you apply for your Non immigrant O Visa in your country they ask for funds in an Australian bank. When applying for my one year extension they were not remotely interested where the funds came from. But as we all know, immigration offices don't all have the same rules.
Do it yourself, I just got a year extension the other day. Immigration speak english, and are so helpful. I took advice from the guys here. They were right it's easy.
What I did was, first night in a hotel. Next day to immigration with a copy of the house book person you are living with id card they asked for their telephone number . TM30 done.
I was in a similar situation. I got the old home bulldozed and it was more cost effective building new. This leaves it up to the builder to organise everything. I didn't retire to complicate my life.