如果雇主申請綠卡已在排期中，但離職了，轉F1身份就可以legally stay in US.
-If you have applied for green card, your application for change of status to F-1 probably may not be approved due to immigant intent.
Can she or he stays in US do nothing (if they can't find a job) until they gets the green card?
-If you only have an I-140, not file I-485 yet, you need to have a legal status to stay in US. If you have filed I-485 in this case, you can stay in US until USCIS make a decision on your I-485. But you had better find a new job in the same field as the I-140 indicated as soon as possible in case USCIS send you RFE for your employment status (if you do not have a job at the time USCIS send you RFE, your I-485 will be denied).
Thank you!
