The lender needs to see that the value of your home is acceptable in comparison with what the guidelines allow for your particular loan program. Some may go all the way up to 95 percent, some may be as low as 50 percent. An appraisal company can be as small as one person working out of the home, or as large as a nationwide network of appraisers. But it all comes down to someone having to show up at your home in person. The wrinkles show up in which appraisers are approved by which lenders.
Some lenders have a list.
Some lenders refuse to use the work of certain appraisers. Some lenders have no list, but simply require a copy of the appraiser's license with the loan package. The job of the loan officer in these situations is to make sure that the appraiser that is used matches up with the lender. Doesn't seem too complicated, but problems can arise due to the variety of policies by different lenders. A loan officer generally will not order the appraisal until you are certain you want to proceed and all the proper pre-qualifying steps have been taken.