When you obtain a mortgage, your mortgage lender will have the right to sell or transfer your mortgage as they so choose. None of the original terms of the mortgage loan can change. The only thing that will be different is who you make your checks out to each month and where you send it. You will sign a servicing disclosure form at closing explaining the lenders guidelines on selling and transferring mortgages and how often they have done it on average, over the past 3 years.

When the holder of your mortgage changes, so will the mailing address for your payments. Lenders are required to notify you of the change but don't depend on them alone: any late payments will still be counted.