...were never married.? Can I buy a life insurance policy for my son's father?
We were never married and he doesn't pay child support.
A friend of mine told me that I can purchase life insurance on him so that if he died my son could get the benefit.

It is often mandated by the courts. There has to be insurable interest which you have with a child. He would have to go through the medical testing so he would be well aware of what you are doing. But I think it is a great idea.