Colorbond Ultra is the only Colorbond steel wall sheeting product that can be used between 500m to 1km away from the waters edge, or if closer, stainless steel roofing and wall sheeting is your only choice. If your looking at buying standard Colorbond sheeting, you will need to be at least a kilometre away from the surf for the sheeting to survive. The same guide lines will apply to fencing products too.
Termites and Asbestos related problems are an expensive issue, that cannot be ignored when looking at a shack to purchase. Termites can make your shack unsaleable and the repair costs can be extreme. Your insurance company will generally classify termite damage as preventable and therefor a maintenance issue, hence no cover. Asbestos containing older houses and shacks built prior to 1984-1985 have the added issue of requiring specialised removal and dumping requirements if any maintenance or renovation work is done to the eaves or wet areas of the dwelling. Considering most houses are likely over time to renovate the bathrooms, this is another expense that needs to be thought of.
If you require further information to the suitability of steel cladding and the environmental implications of near coastal living, I recommend you contact the manufacturers of these products prior to obtaining quotes for building work. The cheapest quote for work, probably does not include the correct recommended sheeting or fasteners.
My web page below has important warnings regarding handling asbestos areas.