Can't tell you much about how it's done, but it is done all the time.

hi there I have a mobile home that I am considering building an addition to. I have found some information on how it is done. small decks and porches are easierthey say. For additions they say to put support below your local freeze line so if the house shifts there will be less problem.

Yes, but you don't "really" connect them. You can make what looks like a connection by filling in the gaps so-to-speak by siding it up to your home, but the addition is actually it's own. You'll obviously need to check with the building codes, but yes, it's done all the time.