It's very common. There are 10s of thousands of leasehold houses in Ireland. If you look at large estates in Dublin on the land registry (landdirect.ie) you'll see estates where lots of houses appear on the same folio - that's because the freehold is all owned by the same company.
We bought one a few years ago, and when we purchased the house I asked our solicitor to arrange to buy out the ground rent at the time. So we completed the purchase, and our solicitor then engaged with the freehold owners (Fitzwilliam Land Securities in our case) who had a standard procedure to follow. There's a formula to calculate the maximum cost, but they also charged a “title search and administration fee” of €302.50 including VAT. We proceeded with that, and got it sorted quickly - so quick that my solicitor was able to register the freehold with Land Registry before they had registered the leasehold (it was a first time registration), so we ended up getting a small refund from land registry.
If you don't agree to pay the admin fee, you can proceed by arbitration, but it can take about a year.
If you don't buy it out, you'll pay a small rent to the holder of the freehold. Mine would have been just under 10 euro every 6 months. Technically you need the permission of the freeholder before you carry out any building works / extensions on the house.
Ground rent is paid on properties that are owned by leasehold. You can buy out the ground rent, so you then own the property outright.
www.citizensinformation.ie