My husband, a permanent U.S. resident inherited his mother's house and some land in Iran . It has just been settled and he is entitled to 50k. When he gets this does he have to pay taxes on it.

There is no US federal inheritance tax. However, there are a few states that impose an inheritance tax on their residents - tell us what state he lives in and we can check it out. I can't speak to whether he owes and taxes to Iran.

Virginia is the state we live in. I know there is no inheritance tax here.

Virginia is the state we live in. Won't we be questioned on the sudden appearance of money in our accounts? And do we declare it as income.

VA does not have an inheritance tax, so no worries on that score.

He may have to file Form 3520 to declare the international wire transfer. There is no tax associated with this- just needs to be declared. See: http://www.irs.gov/pub/irs-pdf/i3520.pdf