Prior to forming his business, Karlan worked as an attorney, first with Covington & Burling and then with the Internal Revenue Service (IRS). While at the IRS, Karlan was drafter of federal regulations relating to 401(k) plans.
Karlan's published works as an attorney include "Differences in Treatment of Employees and Independent Contractors Under Selected State and Federal Statutes," 1998 American Bar Association Section of Taxation Mid-Year Meeting (with Kurt L.P. Lawson) and "Cash or Deferred Arrangements, Matching Contributions, and Employee Contributions," 1998 Annual American Law Institute-American Bar Association Conference (with Mary Oppenheimer).
Karlan founded Professionals in the City to bring the local professional community together and to familiarize residents with the activities their cities have to offer.
On December 31, 2006, when he was simultaneously hosting New Year's Eve Galas at both the French Embassy and the Washington Plaza Hotel, the Washington Post wrote a cover story about Karlan that characterized him as "an expert party guy."
On December 31, 2007, Karlan hosted the farewell party for the historic Hotel Washington, Washington, D.C.'s oldest continuously operated hotel, the hotel located across the street from the White House. With more than 3,000 attendees, this was the largest party in the history of the Hotel Washington. At the same time, Karlan hosted a second Gala at the Embassy of Italy.
In March 2009, the Washington Post published a cover story about how more children of immigrants are seeking partners of the same ethnicity, and how Professionals in the City is catering to this societal change by expanding "its repertoire of lectures and wine-tastings over the past year to include 'speed dating' nights for people of Asian, Latino or South Asian descent." This article quoted Karlan as saying that targeting ethnic groups makes sense in the Washington area, which has more than 1 million immigrants.
In March 2009, in a feature that also included Oprah Winfrey and Suze Orman, ABC News filmed a Professionals in the City speed dating event where it quoted Karlan as saying that credit score dating websites are a double-edged sword because they enable singles to meet other singles who are preselected for certain financial criteria, but that these sites are unable to avoid the situation of singles still having to find a person to whom they are attracted in the first place."
In July 2009, Karlan was featured in a Professionals in the City marketing video promoting its speed dating events, further emphasizing the group's increasing focus on singles.
In August 2009, Nikkei Trendy in Japan featured Karlan and his Professionals in the City speed dating events as what is currently trendy in the United States.
In October 2010, Washington, DC Mayor Adrian Fenty officially commended Karlan for Professionals in the City surpassing a membership of 200,000 in the Greater Washington, DC metropolitan area and for enhancing the quality of life of residents of Washington, DC.
In February 2011, Karlan hosted the nation's first-ever speed dating at an auto show, at which Washington Post columnist Carolyn Hax provided advice on dating and then the speed daters went from car to car in the General Motors exhibit at the Washington Auto Show participating in a different date in each car.
In March 2011, in a feature that also includes Donald Trump, The TODAY Show featured Karlan at a Professionals in the City speed dating event to show how body language affects one's success in dating.
In December 2011, Voice of America aired in China an interview with Karlan about how Professionals in the City Speed Dating events are a popular way in America for singles to meet.
In December 2011, the Washington Post published a story about Professionals in the City is helping build a Jewish social scene in the District of Columbia by hosting events like Professionals in the City's annual Christmas Eve Gefilte Fish Gala. This article quoted Karlan as saying that Jews "who move to D.C. now get involved in 30 seconds because of a Google search, instead of spending three months to find out about each other.”
In April 2012, National Public Radio featured Karlan at a Professionals in the City Speed Dating Event that consisted of 30 men and 30 women dating to show how one's use of pronouns in a conversation determines one's level of attraction to another person.
In February 2014, The Washington Post featured Professionals in the City speed dating events as a key place for older singles to meet potential dates in Washington, DC, stating that Professionals in the City's "series of four- to eight-minute dates is an efficient way to decide who you’re interested in." The article quoted Karlan discussing the various dating challenges people face at different ages.
In February 2014, Voice of America aired in Pakistan an interview with Karlan discussing how Professionals in the City Speed Dating events are a great way to meet lots of singles and find a date for Valentine’s Day.
In November–December 2014, Arlington Magazine published an article quoting Karlan regarding the increase in older singles in the Northern Virginia area, and the resulting increase in options for older singles.
On February 15, 2015, Andrews Gazette published an article quoting Karlan regarding the importance of face-to-face interaction for singles to develop a connection with each other.
Karlan is author of Washington, DC For Singles.
Karlan holds a J.D. from Columbia University School of Law. He holds an LL.M. in Taxation from New York University School of Law. He holds a Bachelor's Degree from the University of Colorado at Boulder, where he was valedictorian of his graduating class.