Given the political-speech context, apartments in an apartment building are less apt than offices in a political party's building. If someone commits fraud or corrupt acts from e.g. the DNC's office, the DoJ doesn't get to collect everything at that building.
Disclaimer: I am not a lawyer. This is not legal advice.
Perhaps the website is the "apartment building" and the accounts on the website are the apartments. In that case, not so obvious.