Legal Question in Real Estate Law in California

Most employment in California is "at will," and the employer doesn't need a reason to terminate the employee. Having a reason is also OK, so long as it is a "good" reason. The main no-no for an employer is terminating an employee for a bad reason, such as because the employee is pregnant, or was a whistle-blower, or joined the wrong religion, etc.

So, the answer is yes.

There are exceptions to the at-will nature of employment, generally created by guarantees of employment contained in individual employment contracts or union collective-bargaining agreements.

Unless he has a written employment contract, he is an 'at will' employee that can be fired anytime for any reason, unless the reason violates the Civil Rights type laws, which this doesn't sound like.