If you are currently in the US and you are applying for a Green Card through an adjustment of status to receive a green card, you can stay in the US (legally) until a decision has been made in your case. However, you are still now allowed to work in the US.
To be able to work while waiting for your Green Card Application to be processed, you may apply for an Employment Authorization Documents (“AED”) with the USCIS.
This application can be submitted along with your green card application or at any time after you have gotten a receipt notice that USCIS confirming they have received your green card application.
If you apply for a work permit in the same package with your green card application, you simply need to include the AED application with your green card application. in this situation, there is no government fee for filing an AED application if it is included in the same package as your green card application.
If you have already submitted your green card application, you can still apply for an AED with a copy of the receipt notice from USCIS showing that your green card application, but you will need to pay the government fees.
In general, the processing time of the application can take about 150–210 days (5–7 months) for the USCIS to process work permit applications.
In case the application is approved, you will be able to start working during the time your application for an Adjustment of Status is being processed.