Check out the government sites and maybe pay for a subscription to IBIS, MatBre.
Here is the Business Entry Point link.
http://www.business.gov.au/Business+Entry+Point/
There is a franchise registry where a lot of information can be found.
IBIS is considered by many to be the best resource for business information in Australia.
http://www.ibisworld.com.au/
The BBB is not really a good resource since they tend to ignore complaints that don't have a lot of media support.
The other good resource, though sometimes spotty, is to run a Google and Yahoo search on the business name and 'forum' and/or 'complaints'
"businessname forum complaint" in the search box.
MSN is the more business oriented search engine in Australia. It's also pricey. Check to see if the business has an entry.
Elven