You’ve probably already covered this base, but I’ve heard that many banks don’t offer mortgages on manufactured homes. A friend of ours “built” (or is the right term “assembled”?) a very cool manufactured home in the desert, but when he wanted to sell it a year or two ago, he found that his pool of buyers was pretty small because they’d have to pay cash. He told us that banks aren’t lending on manufactured homes. This info is obviously based on one anecdote, and maybe doesn’t apply to your situation, but is something to check into.
As far as what else to look into regarding manufactured homes in general, I know that there’s been an influx of new manufacturers in the last 10 years or so, and some are turning out well-designed and pretty sophisticated homes. Of course, the quality varies between manufacturers and much will depend on the final finish work and details added.
You should research the manufacturer of this particular home, and also think about chatting with the contractor who assembled it (if not affiliated with the manufacturer) and those who did the finish work, etc. I assume the seller would understand that there may be more questions than usual, given it’s a manufactured home, and hopefully will have this info readily available for you.