Its a scam. From an architectural engineering standpoint, it would never pass permits.
However, there is a reputable builder that does turn missile silos into underground townhomes. One's been finished and is for sale, but I can't recall the name of the company selling it offhand. My local paper did a Sunday piece on it a month ago.
There was also a company turning old B-52s and jumbo jets into RVs and mobile homes, wingless, of course.