Home sales have been nearly 5 million annually since 2000:
In 2010, new home sales: 323,000 and existing home sales: 4,309,000.
And DOE’s NREL states that home inspectors do about 5 million home inspections:
According to study conducted by NAR (National Assoc. of REALTORS®), “eighty-four (84%) percent of buyers requested a home inspection as part of the purchase contract.” http://www.realtor.org/field-guides/field-guide-to-home-inspections
Almost all REALTORS® (99%) recommend a home buyer to have a home inspection.
Most U.S. homes that are bought and sold are inspected by home inspectors.
That’s at a rate of about 5 million every year (give or take).