If I walk away from a home and purchase a less expensive one (with parents help) can the bank come after the new home equity?

The answer is maybe.  You do not provide all of the needed information. A consultation with an attorney is suggested.  A general response can only state: If you are on title to both parcels and the lender obtains a deficiency judgment against you for the first house, the equity could, ultimately, be at risk.  First, there must be a foreclosure action.  A Sheriff's Sale will be held to transfer title.  Should the purchaser not bid enough money to pay the Mortgage in full, a deficiency is likely.  However, not all lenders seek deficiencies as some counties may require an Appraisal before considering any personal deficiency order.  If such a deficiency is allowed (in such amount as the Court allows), there will be a personal judgment issued. The next step is one of collection.  It may be that your loan was guaranteed and the lender paid in full after the foreclosure.  No one may then look to collect on the deficiency against you.  However, any Judgment is subject to collection.  Collection can take the form of garnishment on your wages, seizure of your bank accounts, or placement of a lien (called a "Memorandum of Judgment") against any real estate titled in your name.  There are ways to avoid such actions.  They can range from Short Sales to Bankruptcy filing.  Considering what is at stake and the potential risk that a subsequent purchase could be placed upon your parents, you should seek out legal counsel.  An attorney familiar with local (as in your county's) foreclosure practices should be able to clearly detail your options and the risks attendant to whatever course of action you elect to take. Any such consultation should occur prior to any purchase of other real estate.