Is such a thing permissible? Or should they inform the purchaser that it is used? Or do they not have to do that, since some purchasers do not ask whether it is new or not?.
He should be sincere and want for his brother what he wants for himself. Of course, if a person sells you something that has been lightly used and has not been affected by use, and he sells it to you as new, that is regarded as cheating and deception on his part. If you do not accept to be treated in this manner by people, then how can you justify doing it to other people?
Based on this, it is not permissible to do such things, unless he explains to the purchaser and says to him: “This is lightly used” or some such.