My husband stumbled upon a website refering to people who make money
taking freelance photos of commercial & residential property,
vehicles, warehouses, etc. for insurance companies and banks.
Presumably they need to keep track of their interest for some reason
and don't have enough adjustors to send out on all the routine checks
that need to be done. This reference also mentioned that the freelance
photo-taker might need to submit a report with the photo. Is this a
legitimate business, and what is this work called by the insurance
companies?

Insurance photography is definitely a legitimate business. However, I
urge you not to pay money to anyone who offers to help you set up such
a business. There are many home business scams out there.

In the 1970s I occasionally assisted a friend who did a lot of
insurance photography. We took still photos of the interiors and
exteriors of buildings from many different angles, and close-up photos
of valuable items. The only "report" that was submitted with the
photos was a notarized statement that the photos were taken on a
certain date, at a certain location, and the names and contact
information of the photographer(s).

My friend who did this kind of work obtained most of his referrals
through an arrangement with a small insurance agency. When the agency
had clients who were interested in documenting their property and
possessions, they would pass my friend's name and number along to the
clients, and arrangements were then made to do the photo sessions.

I do not know what the financial aspects of this business are like,
since I was only assisting, and I was paid by the hour by the main
photographer.