Outsiders to this area might not put the terms "vacant apartment building" and "top-flight investment" in the same sentence. But in DC, the opposite is true, and on Friday, another yet-to-deliver apartment building sold for a big number.

Duball LLC's Marc Dubick confirmed to us yesterday that his firm sold The Swift, a 218-unit apartment complex steps away from the Petworth Metro, on Friday for $75M. Market sources tell us the buyer is an affiliate of Principal Real Estate Investors. The first residents will move in within the next few weeks, Marc says. The sale does not include the revamped ground-floor Safeway and associated parking (which opened two weeks ago and replaced the 50-plus-year-old store that had sat there previously), but does include below-grade parking right under the Swift. It's the second high-profile buy in as many years for Principal, which last year purchased Washington Harbour in Georgetown in a JV with a group of Korean pension funds.

We snapped the project yesterday just before the rains came. Marc calls the deal (which comes out to $344k per unit, by the way) a "win, win, win" for Duball, its partners on the deal (Buvermo Properties with equity and EagleBank with debt), and especially the Petworth neighborhood, one of the city's fastest emerging spots. Duball sold the Swift to avoid going through the favorite acronym in DC investment sales: TOPA, or the Tenant Opportunity to Purchase Act, which requires multifamily owners to let tenants make a competing offer before selling. Cassidy Turley repped Duball in the deal.

Most recently, JBG has employed the same strategy in selling two vacant projects to TIAA-CREF: The Woodley in Woodley Park to for a cool $195M (pictured), as well as the Trader Joe's-anchored Louis at 14th for $170M-plus.