Undocumented doesn’t mean washing dishes for cash.
Your spouse sets up an LLC, which employs you at minimum wage to be a contract worker or consultant. This already happens in government contracting where small companies have a leg up of they are female, minority, or veteran owned.
That's documented though and since the ISA client is working well below the prevailing wage the ISA originator could take them to court/arbitration and prove they're acting fraudulently absent any explanation of why they're working for so much less than they should be.