I'm being somewhat cynical there but it's true nonetheless. Another major factor you need to weigh into the equation are health related issues. There's a lot of formaldehyde and asbestos in those old MH's. I wouldn't purchase anything older than a mid 80's just to be safe and even at that you'll still find some formaldehyde.
Or is it a home you want to purchase? If it's the former then I would recommend you follow Terry's advice and try to secure a chattel loan or borrow from a relative or friend. If it's the latter you won't find any easy way to go.
The best you'll get is a very high interest, short term loan with a very high down payment. Unless the MH is in a very geographically desirable area i.e. a beach, lake, river, mountain resort or on a golf course I'd pass and keep looking.