Corporate Climber?!?
Every time I read a description or synopsis of this film it inevitably describe's Lemmon's character (Baxter) as a "corporate climber," or "corporate go-getter," who lets his apartment out to superiors in exchange for advancement in the corporation.
There is no evidence for any of this in the film. He is anything BUT a corporate climber, or "user" -- in fact, it was merely accidental that he started lending out his place to begin with. At no time are we given any information, or does he say anything that would indicate that his letting out of his place is part of a plan to advance in the firm.
He's just an average guy, not overly ambitious at all. This is why we root for him. Wilder knew what he was doing.