Falling property values are leaving many Americans upside down on their mortgages, which can make it difficult to sell and move.

For the elderly, this problem can be especially grave. RISMedia reports on a husband and wife who are in their 80s and had planned to sell their townhouse to move to a one-story apartment for seniors. But the falling real estate market has made selling difficult and they've found themselves trapped in a home that is not adequate for their needs.They've installed a $7,000 stair lift to make things more manageable, but what about seniors citizens who don't have access to that much cash?

The plight of seniors stuck in their homes illustrates the danger of having too much net worth tied up in a primary residence. By relying too much on home equity in their retirement calculations, some seniors have left themselves in a tough spot. People with enough in savings to absorb a loss on home sale can grin and bear it, but that's not reality for most families whose homes represent their largest assets.