I'm certainly not a lawyer, but I can't find any Federal regulation that prohibits an employer and an employee "agreeing" to have teh employee work 14 days straight. After the 40th hour of the "work week" the rest of the hours for that week are to be paid at time-and-a-half, but I don't see that it's illegal. It might be illegal in some state, but you didn't specify the state.
You say they can't afford to speak up; can they afford it once they get paid for 212 hours in that two week period?