Yes, sous were an old monetary unit; 100 sous amounted to 5 francs; see https://fr.wiktionary.org/wiki/cent_sous I translate by fiver because of this, but 5 francs 150 years ago were a lot more money than $5 today. Then the word sous evolved to be synonymous with money, but in the song it doesn't mean "money" generally, it means a specific amount of money.

Whorehouse sounds more idiomatic to me than "brothel", especially in a popular song like this one; brothel to me is a more refined/scholarly word maybe? But I may be wrong, I'm not a native English speaker.