Central Air - Loft?

Hi, We are looking at an 1800 sq. ft. pre-war loft with windows on only one side of the apartment. Sunday was not that hot, but it was kind of stuffy in the guest room - which was an internal room without windows. The agent mentioned that other apartments in the building have managed to put in central air. Does anyone have any idea what kind of cost we would be looking at to do this? I'm sure there are a lot of factors that would impact pricing - but just wondering whether anyone has any experience with this. Are we talking $20k, $50k, more? Thanks in advance for your responses.