A friend of my friend KB3ERQ used to have a side business "flipping" houses. He'd buy them cheap, do some cosmetic fix-ups, and sell them for a nice profit. Until the housing market collapsed... from what Ben tells me, his friend was going broke making the payments on a house he doesn't live in, that is now "under water" (loan is more than he can currently sell the house for). So he may have to walk away and abandon the house to the lender... which will basically wipe out all the 'gains' he made over the first few years.
That is the risk you take as a speculator, of course. One can presume he knew the risks...