There are a few sites that might help you with this.

Transportable homes in Australia discusses the use and financing of transportable homes & manufactured homes.

Removal homes in Australia talks about the use, sale & financing of removal homes. Typically a 2nd hand home is called a removal home so this is your best bet.

Transportable Home Finance is a specialist mortgage broker that finances removal homes. Has some good articles and links to all the companies that handle the sale of removal homes as well as industry bodies.

Good luck!

CJ