Why does the Federation act as landlord on Deep Space 9? Sisko threatens to collect five years of back rent from Quark in season 4 episode 16, "The Bar Association," as well as power and repair fees. First, shouldn't this be the Bajoran government? And second, what exactly would a cashless society like the Federation be collecting rent for?
The Federation is acting on behalf of the Bajoran government, and Sisko is appointed to run the station on that basis.
Following the Cardassian withdrawal, the Bajoran Provisional Government petitioned for Federation membership, and also for Starfleet assistance in repairing and maintaining Terok Nor. A complex arrangement was established, in which a Starfleet officer would have overall authority in running the station, while the station remained sovereign Bajoran territory.
The subject of the Feberation being "cashless" has come up before, so I won't go into it here, but Bajor is only a candidate for Federation membership, and has only just become free from the Cardassian occupation, so it's unlikely to have become post-scarcity, as the Federation supposedly has.
The Federation is fascist, and much like all fascist governments, they need money to help supplement the use of a cashless economic system (if economics are still a thing)
If you don't believe the fact they are fascist, do any google search online, it becomes obvious after you watch a few videos on it.