Mr. Stern partnered with Largo Investments in the deal at 71 North 7th Street. The pair plans to build a three-story, 15,000-square-foot condo building with retail space on the ground level. Mr. Stern, a Crain’s 40 Under 40 honoree, has teamed up with Largo Investments before, on a site the two bought together on West 24th Street in Manhattan near the High Line. The duo plans to build a condo there