He does not fill out the forms. The employer must file the PERM application for him with the Dept of Labor.
He cannot wait here in the US for this process to be completed. If he is here on a visitor visa he and his family must depart and wait in Mexico while the employer pursues the Labor Certification Application referred to as PERM through the Dept of Labor, and then the employer has to file the Petition for Immigrant Worker with the USCIS. After that is approved then he and his family begin the immigrant visa application process through the National Visa Center's online portal while he is in his home country of Mexico. It can take up to one year for all of this to go through.
It is a HUGELY complex process. Most lawyers who do not specialize in immigration law will not tackle these applications because of their complexity.
I can give you the Dept of Labor website link that goes into detail about the process but it is far from a substitute for a knowledgeable attorney.
The website is currently down for updating.
You can also refer to these websites that give a good over view of the process. It is far to lengthy for me to repeat here for you and there is no simple way to break it down.
Also, the regulations prohibit him from paying for the legal fees or associated costs of the PERM. This is something that the petitioning employer must pay for. You could not reimburse the company for these expenses, either, the law prohibits that, as well.
After you read those links you will see this is a very complicated undertaking and not just a matter of going online and filing out a few forms, it involves the obtaining of the prevailing wage, placing of advertisements to show there are no qualified US workers (that is why experience and training in home country are important, it is a rare skill and if he can show he has this experience and/or training it would knock out many US job applicants); writing recruitment results reports, dealing with the state workforce agency on their listing and referrals and finally filing the online application at the DOL iCert portal.
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