The federal law and state law all set up the minimum wages. If the wage in your contract is lower than the minimum wage, your contract is illegal. If your contract says you could only work for this employer, but the employer did not give you enough work to do for a reasonable living, it is illegal. If you are a full time employee, the state would require the company to provide certain benefits. Pay by hour only provides you the base how to calculate the salary, it does not say the employment is full time or part time.
You should tell the employer that you have a doubt about the legality of the contract and tell the employer that it costs you $9 for coming to work. If the employer does not intend to give you work that day, you would not come.
Don't be afraid. Don't let people take advantage of you because you want to keep your status here. Find a real job, find help in your area in law school clinic or church.
Runan Zhang, Tel: 202-965-4348, website runanzhang.com