Hi Richard,

No, you won't need an Irish licence but it would probably be worth getting an international one. They're available from AAA and you don't need to pass a test. 

On the car front, there's no easy answer I'm afraid. You could try getting in touch with a local dealer near where you're going to be living and see if you can negotiate something with them. They might be happy to set you up with a long-term lease or possibly a personal contract plan (PCP) where you buy the car on credit but can hand it back to clear the loan. 

To be honest your best bet is probably to buy a clunker - something old, cheap and Japanese. Don't spend much to buy it, and either get a friend to sell it for you at the end or drop it off at the nearest car dismantlers on the way to the airport!