The location of Elisa's loft being in SoHo was first revealed in the Series Bible for the first season of the show. Although information in the Bible is not considered canon, this location has not been contradicted by any canon or other canon-in-training sources.
In a Facebook post on September 17th, 2017, Frank Paur commented "The building and apartment were not always so well maintained, neither was the neighborhood, In real estate, timing is everything. Let's just say a lot of hard work went into it. And who's to say Elisa's not savvy about investment opportunities."