To start working in the USA, you need a work permit. There are no exceptions for construction assistants or lawyers.
But it is no secret that the US Internal Revenue Service (IRS) is not “friendly” with the immigration service (USCIS). Therefore, many immigrants start by getting an SST card and EIN (individual taxpayer number) and looking for work.
Bad sign
If you are offered a job for $30 to start as an assistant, 60 hours a week and do not require any documents (EIN, SST), run. Firstly, you will not be paid that much. Secondly, most likely, they will not pay you at all.
If you are offered a job for cash, run. When you are offered a job “for cash”, most likely, the potential employer is not just not clean in terms of tax issues (this is not your problem), more importantly, he does not have workers compensation and disability benefits insurance. This means that if something happens to you on a construction site, it’s your problem. And healthcare in the US costs money if you don’t have health insurance.