Where to buy used/cheap gold?

Hi all,

My dad used to be a gold smith but now retired, however he is seeking to continue his work for friends and family.
He told me his old company and a few aquaintences often attend auctions or sales where they can buy gold for cheap - sometimes this gold is dust or poor quality and than they purify to make 18 or 24 ct gold.
I was wondering if anyone knows where one of these places are?
I'm in VIC btw.