The buyer has need of a hundred eyes, the seller of but one warning to a purchaser that it is their responsibility to examine goods on offer. Recorded from the mid 17th century; a similar saying is found in Italian.
let the buyer beware it is up to the buyer to establish the nature and value of a purchase before completing the transaction. Recorded in English from the early 16th century. The Latin tag caveat emptor is also found (in full, caveat emptor, quia ignorare non debuit quod jus alienum emit ‘let the purchaser beware, for he ought not to be ignorant of the nature of the property which he is buying from another party’).