Why is this woman built a house? And why is her base already there?
One more time.
The Jews went to Babylon for 70 years.
When they returned, they brought bad habits with them from Babylon, they had Babylonian wives. Ezra made the men divorce their wives.
In a nutshell, the Jews returned to Jerusalem, Zechariah is writing to those Jews who returned, the basket of iniquity is taken back to Babylon, it represents the false idols, immorality, etc.
Babylon was a pagan country, so the house that was already there, was probably whatever pagan gods the Babylonians worshipped.
None of this has anything to do with the first century, or the yet future, it's all ancient history that pertained to the Jews, Babylonian captivity, and the Jews return to Jerusalem after the captivity to rebuild the temple.
Not sure why you think this has anything to do with Rev 18