Is the husband sinful for having a veiled Muslim maid in his house without a mahram, knowing that the maid was brought through a recruitment office and he does not need her mahram and cannot provide him with accommodation and a salary?

It is not permissible to bring a maid without a mahram, whether through direct agreement or via recruitment offices, because it is not permissible for a woman to travel without a mahram. However, since she has already arrived, there is no harm in her staying for service, provided that she has a separate dwelling.