Depends on where you are? If you don't have to fly, why not bring the car you have with you? You will buy a car cheaper in pretty much every other country in Europe? (Except Denmark) and drive it in Ireland VRT free as long as your not a resistant of Ireland for 6 months.
However if your not able to get the car to Ireland, you should be able to pick up a cheap runaround for under 1000 euro I would say. But you will need to tax for 6 months/nct for 2 years/insure it for a year.
Not too sure if you've you can transfer your insurance to an Irish Reg Car for 6months, would need to contact you insurer.
Try to buy a small engined Japanese car (mirca or starlet) because road tax is expensive over here. and has nct already done.
Hiring a car for 6 months would be crazy money.