Thanks for the question! I'm glad you are looking into possibly using your VA loan benefits for a home purchase. They do have several advantages and differences from a conventional mortgage. The VA does allow financing on certain manufactured homes, but does require that the home be built on a permanent foundation. The difficulty is in the definition of "certain manufactured homes" and it's a complex one - involving state and local laws. Because of this complexity, USAA does not lend VA on manufactured homes or mobile homes.
Many of the larger/national lenders do not either for similar reasons, but there are a variety of niche lenders in the market that meet this demand.