Non-Resident Income Tax

A friend is an Irish citizen long resident abroad. He earns a salary and pays tax in his (EU) country of residence. He also has Irish rental income.

Is he liable for Income Tax on the rental profit, for PRSI, for USC?

Can he claim tax credits ?

He has an agent in Ireland collect the rent for him.

Are there any other issues due to his being non resident the he needs to be aware of.

Thanks