You got pre-approved for $400,000, so you find a $395,000 house and feel safe. Then you max out your credit cards buying furniture and making improvements before closing. Lenders do a final credit check right before signing, and a dip in your credit score or new debt can kill your approval. Even soft inquiries or new accounts can raise red flags. Keep your finances frozen from pre-approval until after you've closed—every late payment or new debt is a risk.