“The former.” The former “house” was Solomon’s temple.
“prosperity.” The standard rendering of the Hebrew word shalom is “peace,” but it means much more than that; it means peace, wellbeing, wholeness, prosperity. Especially in a context like this, “peace” is too limited. God is promising that in the future Jerusalem there will be shalom, prosperity, wellbeing. Of course this could only happen in a time of peace, so peace is certainly included. There are many prophecies of the prosperity and wellbeing in the future earthly kingdom of Christ. The NRSV and Roterham’s Emphasized Bible also say “prosperity.”