Dustin Hoffman delivers a truly remarkable performance as “Ratso,” making this my favorite of his roles. He’s paired with "Buck," a stylish but inexperienced man who comes to New York intending to make money, only to find himself being paid by the woman he's supposed to be servicing! Initially, “Ratso” takes advantage of someone just as naive, but over time they begin to rely on each other—a fortunate development for “Ratso,” considering his precarious health. His constant cough is made worse by the terrible conditions in which he and later "Buck" are forced to live, along with their overall poverty. It's a wonderful narrative, and John Schlesinger directs it with considerable flair. The connection between these two characters feels genuine and honorable, despite them not exhibiting those qualities when dealing with anyone else; “Ratso” would likely scam his own grandmother if he got the opportunity. Their relationship is believable and heartfelt—without any unnecessary sentimentality; and Waldo Salt’s writing makes sure that the dialogue, even though it's often brief, manages to be both touching and funny.

Source on TMDB