Not high, if you’ve stayed within your budget, but it does happen. Remember that pre-approval is a statement that you are considered generally qualified to pay back a mortgage, whereas the actual mortgage approval is on a specific purchase. The lender may believe that you are paying too much or may have uncovered liabilities that they did not find in the pre-approval. Also, if you are not able to pay a certain percentage of the cost in a down payment, typically 20%, then you may have to purchase mortgage insurance, which increases your costs. You don’t have to stay with the lender that gave you pre-approval, so you can consider applying elsewhere, which is a good idea in any case.