I think it’s fine to have friends of the opposite sex. Though I think that you should meet either through friends, family or work. I don’t think it’s appropriate to randomly go up to a stranger looking to become friends. Maybe if they tell you right away that they only want to be friends. Also they should tell you they are married right away. I’ve had this married man approach me multiple times to talk and he’s never mentioned he was married. Also no wedding ring. People have told me he’s married. I can’t tell if he’s just being nice and wants to be friends or if he’s expecting more. I just don’t think his behavior is appropriate.