Sparrow,
I know you want to be a loner in this adventure of yours, however, unfortunately thats just not possible.
Are you an Australian citizen? I assume not.
In which case, as a foreign national buying land or property in Australia you are subject to FIRB (foreign Investment Review Board) standards.
One of which means that you can only buy vacant land if you commence building a sitgnificant dwelling within 24 months.
Although my previous suggestion was slightly sarcastic, you really need to speak to the experts if you plan on buying real estate as a foreigner.
http://www.firb.gov.au/content/real_estate/residential/for_development.asp
Also, as a foreign national you will need to apply for approval via a solicitor.
I am a real estate agent specialising in selling multi million dollar lifestyle property (yes, even in "this" market) to both Australians and foreigners.
If you plan to buy land here you will also need to seriously consider building on it.
Given you are in to Silver only and you plan to transport your stack by car and bury it manually I assume you have under 200kg of silver? (otherwise youd need good suspension in the rental car you pick up at the Airport)
Eitherway...your costs involved with "storage" by building a house could possibly outweigh the value of your silver?
Do your research a little better than asking forum members.
You will need tospeak to experts in real estate. I dont intend to sell you anything so thats why I am taking the piss but you need to understand that your lone-ranger approach wont work.