Conflict of interest/collusion in academic scenario I know somebody, let’s call him Joe, who had been a good student. Being a good student, other students asked help from him to understand the class materials. In the meantime, our university started recruiting a lot of international students. These new students, especially those who had a lot of money started hiring Joe to teach them for a fee.

Then, I came to know that Joe charged these students a set fee for the semester with the understanding that they would get the expected grade. This means that he would do online quizzes, do any specific homework problems that students had difficulty, and teach them before a major exam.

Then, Joe became a teaching assistant and now he has access to more materials that normal students may not have. Since he is now a graduate/teaching assistant, he could potentially have access to quiz/exam questions before the exam and have answer keys for those tests. He continued to assist other international students for a fee.

Now, Joe is at part-time professor. He finished his graduate degree and the university hired him for part time teaching. He is continuing to help with quizzed, do homework and possibly leaking exam questions for other students.

In future, he may be hired as a full-time professor at the university. 

Personally, I know this, and I do not feel this is right. I see a case of collusion and conflict of interest with this setup. 

Should I inform the university about things that is going on? I am not sure if university knows about all the things that are going behind the scene.
If this is a real, rather than a hypothetical, then yes, Joe has been unethical and probably criminal, though it might be hard to make the case. 

In theory you should bring it to the attention of the authorities, but you will be creating a painful situation for yourself, conceivably being charged with slander. An anonymous letter to authorities would be safe, but easy to ignore. 

A group of accusers would be more likely to be heard than an individual. A complaint transmitted by a trusted authority such as a lawyer would be relatively safe and the lawyer could advise you on your potential liability. 

But the charge is a serious one.