Here's your answer. It's ...

Mon, 11 May 2009 18:25:00 GMT

Here's your answer. It's a Q and A that is about financing manufactured homes built prior to 1976, but it's the same reason insurance companies may not insure homes built prior to 1976.

http://www.bankrate.com/brm/news/realestateadviser/20081207-mobile-home-lending-standards-a1.asp

Zillow Advice: Buying Foreclosures - why won't insurance companies insure manufactured homes built before 1976