Condition? Amenities? Quality? Access? North of Benning? South?
Too may variables to give a fair answer. You could try Zillow or Eppraisal or RealQuest or some other web site to get an answer, but the best of these are not good enough. You'll need an agent to review the property and run a Comparative Market Analysis of properties that have sold recently.
OR, you could hire an appraiser. The appraisal for a multi-unit will probably cost about $500-$750 depending upon experience and competence. Make sure you hire someone who has experience in the Kingman Park area and can honestly and truthfully evaluate the property, not someone from the burbs who thinks that a garage is worthless and square footage is the only guide.