selling a house for less than you bought it...

[Account Closed]

with house prices dropping dramatically Im just curious as to what happens with a mortgage that is worth much more than the houses purchase price once you sell it? the buyer pays off part of your old mortgage but is the balance on your end then due immediately in ALL cases? I guess it would essentially be a short sale but Im wondering if you can sell a property for less than you owe while continuing to make payments on your old mrtg without paying it in full- you were never late and you dont want to foreclose but you just have to sell and can only get a certain price...