What it means
Caveat emptor means "let the buyer beware". Traditionally it placed the risk on the buyer to inspect goods or property and satisfy themselves about quality before purchase. In modern Australia this principle is heavily qualified by consumer protection. The Australian Consumer Law implies guarantees about quality and fitness, and bans misleading conduct, so sellers can't simply rely on caveat emptor. It still has real force in some areas, such as buying property, where buyers are expected to make their own inquiries.
How it's used
The agent reminded the buyers that caveat emptor applies, so they arranged a building inspection before signing.