The person about which you speak has a choice: keep working for the wages he is being paid or quit and find another job. As long as the employer pays for all of his time at minimum wage or higher (including overtime when due) the employee has no way to force the employer to pay more because it is fairer to do so.
As to the overtime not being paid, there are several ways to deal with that situation.
First, he can do nothing for the time being except to keep track of all of the overtime he is working. Then, after he finds a new job, he can make a claim. That approach assures him that any possible retaliation will not end a job upon which he is financially dependent.
Second, he can make a demand to be paid the overtime. He should do this in writing if that is the approach he takes.
Third, he can have an attorney write a demand letter to the employer seeking the back overtime.
Fourth, he can file a small claims lawsuit seeking the prior overtime.
Fifth, he can file a superior court lawsuit seeking the prior overtime and an order that the employer pay him overtime going forward.
Sixth, he can file an administrative claim with the Labor Commissioner's Office, also known as the Division of Labor Standards Enforcement.
There are many options and each have their strengths and weaknesses. His best approach would be to locate and consult with an experienced employment law attorney as soon as possible to explore his facts and determine his options. I would suggest he look either on this site in the Find a Lawyer section, or go to www.cela.org, the home page for the California Employment Lawyers Association, an organization whose members are dedicated to the representation of employees against their employers.
Good luck to you and to him.
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Concerning unpaid overtime: File a wage claim with the State - very effective (please see the post at the link below).
Concerning hourly pay: As long as he is being paid at least minimum wage (which apparently is the case), the amount is a business, rather than legal, issue. A lawyer is not likely to be especially helpful. He is free to try to negotiate higher pay, and to look for a job elsewhere that will pay more.
This information does not constitute legal advice and does not establish an attorney-client relationship.
If you are an hourly employee you are entitled to receive overtime pay over 8 hours in a day or 40 hours in a week... An employer does not have give an employee a raise if they don't want to. I think he should quit this job and go to the Labor Board and file a claim and try to have them help get his overtime paid. You don't need an attorney if you go to the Labor Board.