Another common mistake is applying for a new credit card, or financing the purchase of things during the mortgage loan process, like buying a car, or new furniture. Changes like these can drop credit scores, and increase debt ratios, which can cause a higher rate or worse.

Changing jobs can be a good thing, but usually not in the middle of processing a mortgage loan, especially if the change is to commission based pay, a different line of work, or self employment. Lenders want to see a stable source of income showing a history of at least 2 years of earnings.

Borrowers who plan to refinance their current mortgage, or take cash to pay off other debts, sometimes assume that they don't need to make any more payments on those loans. If the payments go past 30 days late, especially the current mortgage, there may not be a new loan.

Sometimes liabilities that were not listed on the mortgage loan application appear later in the title report, which may include: tax liens from unpaid taxes, mechanics liens from unpaid contractors, a judgment from a lawsuit, and even a second mortgage that did not appear on the credit report.