1)
What do we learn from "they will build houses and live in them..."?
1.
Radak: They will live as long as the house stands, and longer, like verse 22 explains. Similarly, "they will plant vineyards and eat the Peros" as long as they bear fruits.
2.
Malbim: Since they will not die prematurely, those who build houses and plant vineyards, they themselves will live in them and eat the Peros.
