There is no way to save equity from a home that is foreclosed upon. In order to reach foreclosure you have to breach the loan agreement that was signed with your bank. Once that happens, you risk losing all rights to the home, which is being held as collateral against the money the bank lent you. That being said, the foreclosure process is not immediate, and assuming there is adequate equity in the property you may be able to do something to avoid the foreclosure.

Typically foreclosure is started by falling far enough behind that a lender will trigger the foreclosure. This normally happens once you are 90 days or more past due. If you believe that this is likely to happen to you, and you have equity in the property you can attempt to sell the home. If you can sell before the foreclosure is finalized, while you are still the owner, you will be left with the difference between what you sell for and what it takes to payoff the loan.

On the other hand, once a foreclosure is finalized, the bank that lent you money to buy the home has essentially repossessed the home and is now the owner. As the owner to the property they then have the right to sell it, and are entitled to any gain on the sale of the home.