The knock with a modular is that if the owner decides to sell it after he eventually builds a permanent home to take it's place, he will take a beating.
*They typically do not hold resale value well.
At least around here they don't hold up too well, guess maybe because there are so many of them?? Now if he decided to keep it for one of the kids to move into later on, or the inlaws/guest house that would be a good move. If you're going to get a "mobile" type home, then just go ahead bite the bullet and get a cheap, used one. I know, it will not help you with any style points, but when/if you go to sell it, you won't have much in it to lose. jmho.....