Anytime consumers open new credit accounts -- credit card, auto loan, etc. -- their FICO score could drop, according to Craig Watts, a spokesman for Fair Isaac, the creator of FICO scores.
"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