FHA has no problem insuring single wide manufactured homes. The problem is that the FHA lenders, as of the writing of this blog, will not touch them. Even with the FHA insurance, the lenders won't touch them. Very few non-FHA lenders will touch them either. My list of single wide lenders is down to about 4 now!
My best guess is that historically, people that purchase single wides are less well off and more suseptible to financial peril the the rest of the home buyers. Secondly, the single wide manufactured homes probably depreciate more than block homes and double wides. This makes it easier for the borrower to get "up-side-down" and more apt to walk away from a bad investment. Finally, if a lender is taking back, through foreclosure, a vastly higher percentage of single wides, it is simple math.
If a buyer can put a good chunk down, to protect the lender from depreciation and to give the borrower "something to lose," there are some ways out. Right now, in Florida, we need at least 20% down. And I cannot help people in other states, sorry.
Double wides? All day long! They are easy to go FHA with a 3.5% down payment and some closing costs.