Caveat emptor
Etymology
A Latin phrase meaning "let the buyer beware," from caveat, the subjunctive of cavere, "to beware, to take care," and emptor, "buyer," from emere, "to buy, to take." It captured the common-law default that the risk of hidden defects fell on the purchaser. Modern consumer-protection law has steadily eroded, but not erased, that starting point.
noun phrase · /KAV-ee-at-EMP-tor/
The principle that a buyer is responsible for checking the quality of what they buy before purchase.
What it names
The old rule behind "sold as seen" — why inspecting a used car or a house is on you, not the seller, unless there was outright fraud.
Example
He learned the meaning of caveat emptor when the "restored" antique turned out to be a modern copy.
Related idea
Caveat emptor puts the risk of a bad deal on the buyer; a fiduciary relationship flips that, requiring the stronger party to protect the other.