Best of luck,
This is where the real lending process happens. A simple pre-approval letter, once deemed to be adequate does not mean the buyer can actually get the loan, and the information gathered and the process of underwriting will actually determine if the buyer can buy the property or not. Today, there are a lot of deals killed in the underwriting process.
By being pro-active, prompt and cooperative, you and your agent can help to move the process along in a timely manner.