回复：回复：if you're EB I-485 approved..

I don't know exact time, but "following-to-join" means applicant needn't wait for immigration visa avaiable - this usually takes 3-7 years.

It all depends on the processing time at US Consulate in GuangZhou. It may take 3 months to verify your status and another 3-6 months waiting for the interview appointment....

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http://uscis.gov/graphics/howdoi/Appproc.htm