Is it credible for others to ask you for help in applying for a patent?

That depends on what kind of person he is. According to the law, only practicing patent agents (later referred to as patent agents, only in a different form, or doing the same work) can not apply for patents during their practice, and others have no restrictions. If you can't apply in your own name because of your professional status, it's ok. Others generally don't apply for patents in the name of others.