Verse 18 is the logical conclusion of verse 16. Amulek was cut off from everything, and had no home and no kin. Alma provides him with that, taking him "to his own house." Mormon would have been particularly sensitive to this type of issue, so he makes sure that we have the important conclusion to the story. This man who was bereft of his support network nevertheless finds a new one in Alma and the gospel. So too do many modern saints find themselves bereft of their former social supports, and find replacements for them in the Gospel.