Many mortgage lenders sell mortgages to other companies, or transfer them for to them for processing. You have a right to know if they're going to do this, and in fact the lender has three days to tell you once you've applied for the loan -- just as they have to give you a Good Faith estimate and make their fee structure transparent.
It's critical that you provide you mortgage provider with detailed and accurate information about your credit. Credit problems discovered later could delay the loan, or torpedo it altogether. Clean up your credit beforehand, or the loan process may take more than the average of 45-60 days.