As well, the Irish Tourist Board has some very informative publications. For Northern Ireland, get the annual Where to Stay in Northern Ireland guide to hotels and guesthouses from the Northern Ireland Tourist Board . The difference is that a guest house must have at least five bedrooms for rent. A large guest house is pretty much indistinguishable from a small hotel. A town and country home or farmhouse may have fewer than five bedrooms and can be more intimate - you will often have breakfast in the proprietor's own dining room, and they will invariably take a personal interest in your journey.
Hotels have certain advantages though.
A third option is to rent an entire house or cottage. There are some wonderful properties available at very reasonable prices, but the obvious disadvantage is being restricted to the area in which your cottage is located. The Irish Tourist Board produces a comprehensive publication called Ireland Self-Catering Guide which lists all of the houses available and gives details on how to book. Bookings are generally made by the week. What It Costs Budgeting is a very personal matter.