Not sure why this is considered an innovation - prefabricated mobile homes (aka trailer park housing) have been around for a long time. 
The reason that his business is not booming because in most areas with a housing shortage, the problem is the cost of the lot and getting a connection to utilities (water, sewer, electricity etc).  These add up to way more than the $40,000 quoted in the article.  Also, it is much more difficult to get a mortgage and most municaplities will not allow them in most neighborhoods..........