Does sin befall the seller of youthful T-shirts (half-sleeved) if he sells them to women who might wear them themselves?

There is no sin upon you for selling women's clothing, unless you know or it is highly probable that the buyer will display herself immodestly in it. In that case, selling it to her becomes forbidden, as it constitutes aiding in sin, in accordance with the Almighty's saying: "And do not cooperate in sin and aggression." Similarly, it is forbidden to sell men's T-shirts to women if you know that she will buy them for herself, as this involves imitating men, which is forbidden; for the Prophet, peace and blessings be upon him, said: "The Messenger of Allah, peace and blessings be upon him, cursed men who imitate women and women who imitate men."