Who would we have thought will live in the houses that they build?
Malbim: The heir, or a stranger.
Why does the verse teach also about planting?
Malbim: Trees last longer than buildings.
Why does it say "Ki chi'Ymei ha'Etz Yemei Ami"?
Rashi citing Targum Yonasan: This refers to Etz ha'Chayim. Radak - perhaps this refers to what it says in Yerushalmi Brachos 1:1, that the Etz Chayim (in Gan Eden) is a 500 year journey [thick].
Radak: Others will not live in the house that they build, because they will live as long as the trees that they plant - "they will plant and another will eat." It says "Ami" and "Bechirai", for only they will have this longevity, but not other nations; it will be wondrous.
Why does it say "u'Ma'ase Yedeihem Yevalu "Vechirai"?
Radak: What they produce will wear out in their lifetimes. This is like "they will not build and another will live in it."
Malbim: They will live longer than the trees that they plant.
