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Normally, when the I-130/I-485 is sent, you have the option to also request an EAD (employment authorization) via I-765, which takes a few weeks to process, while the rest of the I-130/I-485 can take months. The alien can then work on the EAD while the petition is still pending.
But at this time, you say that the greencard has been approved. So the EAD is not really an option, as it is meant to provide a temporary SSN while the petition is pending. Therefore, the only real viable option is to request an appointment with INFOPASS and ask the agent if they can provide some kind of temporary employment authorization until the greencard comes.
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