disclaimer: IANAL (I am not a lawyer!), so any advice I give is merely anecdotal common sense, not actual legal counsel
Your risk is minimal. Legal authorities (if it is deemed illegal) would go after the dude at the top of the pyramid, not the subcontractor who did some designs for the developer who built their web interface.
But beware, if their business is illegal, then you accepting money from them directly or indirectly could result in some unwelcome consequences, if they are ever investigated.
If you have the luxury of saying no to this job, then say no and move on.
And don't get yourself sucked into a MLM scheme - they are usually a financial money pit for the gullible, greedy, and desperate.