It is permissible to work for a disbeliever in jobs other than being a servant. It is not permissible for a Muslim to be hired by a disbeliever to do something that is not permissible for him to do, such as pressing grapes for wine, tending pigs, and so on. It is stipulated that he must adhere to Islamic rulings with regard to greeting others, offering condolences, offering congratulations, and so on. The basic principle is that it is prohibited to work in a mixed environment, because of the many evils and transgressions that result from that. The matter is more serious if that is mixing with the disbelievers, because there is a great deal of immorality and illicit relationships among them, and they talk about such matters.