Jordan herself makes it somewhat clear where she could possibly be living. She tells Nick, in chapter three, after her hour long meeting with Jay Gatsby in the library:
“Please come and see me. . . . Phone book . . . Under the name of Mrs. Sigourney Howard . . . My aunt . . . ”
Nick also recounts their meeting in the tea-garden at the Plaza Hotel which suggests that she lives close by. Because most of their meetings occur in and around New York, the address that Nick has to find under her aunt's name is, more than likely, one in Manhattan. It is easy to assume that Jordan should live in a wealthier part of the city, in a place central to her general comings-and-goings. She hobnobs with the wealthy and, therefore, has to subscribe to the accepted style and living conditions of those she associates with.
One cannot help but suspect that Jordan is a sponger - one who lives off the generosity of others. This is supported by the fact that she does not have her own apartment. We do not know whether she pays any rental but can assume that her aunt should be of the means to provide rent free accommodation to her famous niece. Furthermore, when Nick meets her for the first time, she is visiting at Daisy and Tom Buchanan's huge mansion. She also seems to be attending parties constantly and has admitted to loving large get-togethers since they are so 'personal.'
Added to that, it does seem somewhat improbable that her career as a professional golfer can generate the type of income she needs to support her lifestyle. However, she is famous and the rich are more than likely happy to welcome her into their company.
It is ironic, then, that Nick should have such a keen interest in her and even to believe that he loves her, since she is the epitome of those he so mercilessly mocks. He constantly ridicules those who attend Jay's parties but obviously sees her differently although he does acknowledge her penchant for lying.