The Mobile Homes one is a fake story made up by Snopes for their TRoLL section. It's not true. There was no business called Sweet Homes in Mobile, and the prefab housing industry did not originate there.

Manufactured houses really did grow out of the camper/trailer industry. The name "mobile home" is a holdover from when they had wheels. The first companies to deliver prefab houses to set on foundations already had thriving businesses making trailer-homes or other prefab structures (like those seen on construction sites)