RW hit the nail on the head with that. Another caveat to what RW noted is that, in a foreclosure situation the 1st lien holder (the mortgage company) gets paid first, and if there's any left, the 2nd lien holder (the company that holds the HELOC or 2nd mortgage) gets paid, and on and on until anyone who holds a lien on the property get's paid. In a lot of these cases there isn't enough money after the foreclosure to even cover the 1st lien holder, the 2nd gets nothing, etc. Additionally, and I've seen this a lot down here, people that bought houses before the real estate boom and only took out 1 mortgage soon saw that their property was worth a lot more than the balance of their mortgage, so they took out HELOCs and did cash out refinances, also avoiding PMI.