"Hence the admonition to not open other new accounts while your mortgage application is in process," he said.
A big purchase would use up a considerable proportion of a borrower's total credit limit, which results in a drop in the score. Lenders often continue to check credit scores in the weeks before closing.
"The lender will likely slam on the brakes if the applicant's credit scores have suddenly dropped below the minimum required for the requested loan rate," Watts said.
NEXT: 3. Skimping on home inspection