Can you explain to me the differences between "help" and "favour".

He helps his friends.

He does his friends favour.

By the way, I suppose that he is a generous man. Is the sentence below natural? Or can you suggest me a better sentence that best convey the ideal that he is generous?

He help his friends and he don't need they repay him.

Thanks in advance.
james doHe helps his friends.
He does his friends favour.
He helps his friends. (always, regularly) He helps whenever he sees that help is needed.
He does his friends a favour. [Normally this would not be in the present tense.]
He did his friends a favour. (once, on one occasion) He did one specific thing for his friends. Maybe he let them use his phone when theirs was not working. Maybe he lent them some money in an emergency. Maybe he drove one of their children to school when they could not.

If you want to say that the man is generous, that's all you have to say:

He is a (very) generous man.

To clean up the sentence you suggested, however:

He helps his friends, and he doesn't expect them to repay him.

Thanks CalifJilm.