Okay, here is what you will typically see.
1) the MH's are titled and you only take the title [chattel property] - you have no interest in the land, just the MH.
2) the MH's are titled and you take the title [chattel] and the land [by Deed/Mortgage/whatever your state calls it] - your security consists of both the MH and the land.
3) the titles to the MH's have been retired, making the home a part of the Real property. Your Deed/Mortgage is your security and you have an interest in both the MH and the land.
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My opinion only. Not legal advice.
Say you'll haunt me - Stone Sour