Can you walk away from new construction at closing

[EJ K.]

Wife and I are building a new home. We had to place a 3 percent deposit. Builder is financing it up front. We are securing with loan at end... 

Can we walk away if the market crashes and better deals open up? I know we will lose deposit. But can the builder come after us for more? I’m saying without cause other than value had plummeted. 

Any info is appreciated .