If he works for the company that is sending him to a different place, ie not starting a new job, they may be able to help you guys figure out what to do. A lot of my friends that work for Conoco-Phillps can't sell their homes for the amount the owe and the company buys them then sells them later. They even have Realtors come in after the buy out and update them to fit the market.
I wish I knew of a way for this to work out other than telling you to just rent the current house out to someone.
The other option is to do a lease purchase. We did that one time and it was wonderful. The house was in our name with a lien against it, filed in the court house, and as long as we made our payment everything was fine. The money was going towards to agreed upon plan, $375 per month for 18 years. No interest, no refinancing, nothing. We could pay it off early if we wanted to but it would be for the full amount. Since it was ours we could do the same as if we were using a bank.
It was a 3 bedroom 1 bath brick home with lathe and plaster walls. Pretty old, maybe the 40's. It had a half basement for storage and laundry. It was comfortable and secure in a storm.
When hubby got laid off at Conoco-Phillips we had no income for about 6 months and all the money went bye bye. We lost my new van, our credit cards, credit ratings went out the window, etc...we got behind a month then another.
The guy who was financing it for us sat down and told us what our options were. We could try and get a loan and buy it outright, make the 2 payments and catch up, or let it go. We decided to let it go back to him. We lost nothing, if we had been renting it would have cost more. It was a good experience for us. The house resold a month or two later and she is still there. The house doesn't look as nice as when we lived there but it is 20 years older.
So, if you sell at a loss, can't sell your home, or decide to hold on to it. There are options. The market should pick up some day.