They are not always visible from the road, these large old houses with long histories and uncertain roofs. Some have remained in family possession, but others have changed hands several times in recent years. Who lives in these large houses now, and how do they manage to make enough of an income to remain in residence there?

Eithne Jarrett, Killinvoy House, Co Roscommon

`There was no back door on the house, so the wind and the rain had blown in," Eithne Jarrett recalls of Killinvoy House at Knockcroghery, Co Roscommon which she and her family moved to in 1992. "But it was a strong, solid house."

They were able to arrest the decay in the three-storey Georgian house over basement, built in 1825, which had served as the local rectory for over a century. During the Civil War, local people were given shelter in the house. It then remained in the possession of one family, the Jacksons, for 44 years. From 1986 until the Jarretts bought it, the house was unoccupied.

The Jarretts had come home from England, where Eithne had been working in healthcare management for the NHS. "There wasn't anything for me to do locally of the type of work I had been doing," she explains, "so I thought it would be a good idea to use the space we had here. The basement cellars are huge. I tried to think what use I could put them to. Eithne had always made her own preserves, and she hit on the idea of producing them commercially. She spent two years developing recipes and, with the help of the catering college in Cathal Brugha Street, came away from there in 1995 with seven prototypes for jams, marmalades, pickles and chutneys.

When they were clearing out the basement to put in kitchens, a packing and storage area, the basement yielded up some strange booty. "We found lots of bird skeletons, and old glass bottles still with their stoppers in." They also found an oil painting of "a very creepy gentleman with piercing eyes", and a box of letters and photographs.

Eithne named the business, Aisling Preserves, after her small daughter who died several years ago of cystic fibrosis. It flourished from the beginning, helped by the support of her local Teagasc branch, the Roscommon County Enterprise Board, the Business Innovation Centre, and the National Food Centre.

Killinvoy and its large empty basement was essential to the existence and success of the business. "If we hadn't had the house, I'd have had to rent the space to work in, and there would have been huge overheads. It would have been impossible to set up if we weren't living here." Eithne now produces about 200,000 jars of preserves, pickles and chutneys a year, and employs five people.

"I'm expanding all the time; I've just bought a filling machine and a shrink-wrap machine." Her biggest seller is Whiskey Marmalade, but the Rhubarb and Ginger Jam, and the Apricot Jam with Whiskey and Almonds are also very popular. Her biggest outlet is the chain of Super-Valu shops. Apart from that, she supplies delicatessens and craft shops around the country. Her biggest individual outlets are Locke's Distillery in Kilbeggan and the Wrights of Howth shop at Dublin Airport.

Eithne Jarrett is modest about her success. "People in the west are tough and resilient. They have to think up great business ideas to survive."

Prue and David Rudd, Busherstown House, Co Offaly

Prue and David Rudd moved from Dublin in 1973 to Busherstown House in Moneygall, Co Offaly. Bushers town dates from the 1730s; a Gothic revival house with a crenellated roof. "It's a big solid house and we occasionally get a leak, but we patch it up as it happens," Prue Rudd explains.

The Rudds were successfully pig-farming in Offaly, until the market collapsed in the early 1980s. They hit on the idea of producing their own pork and bacon, which are low-salt, antibiotic and hormone-free. "We built cold rooms within the old kitchens downstairs and used the butler's pantry as a packing room."

Similar to Eithne Jarrett's experience, the space within their property enabled the Rudds to go into production without huge overheads. Teagasc, Bord Bia, Shannon Development and the Offaly Enterprise Board supported them. Three months ago, the business moved out to a factory unit in Nenagh. It now employs eight full-time and three part-time staff.

While the Rudds run the pork and bacon business as a duo, five years ago Prue established the Busherstown Creative Centre as her own initiative. "I converted a stable block at the back of the house into a big studio space," she explains. Day and weekend classes take place there.

The autumn schedule for this year includes silk painting, feng shui, homeopathy, stained glass, decoupage, basket making, gardening, and furniture restoration. "The next plan is to convert the area we used for the pork and bacon production into accommodation, so we can offer residential courses," says Prue.

Sharon and Jeremy Kenny, Middleton Park, Co Westmeath

In the 1980s, Middleton Park in Castletown Geoghegan, Co Westmeath came to national and international attention. In a headline-making story, the then owner, professional gambler Barney Curley, raffled the house for tickets at £200 each. The sale raised £1.9 million, a huge sum at the time.

In January of this year, Sharon and Jeremy Kenny moved into Middleton Park. The house was built for the Boyd Rochfords, and the conservatory was built by Turner, who also designed the Botanic Gardens. Some of the ceilings are by the famous Francini brothers. There are nine bedrooms in the main part of the house and 16 in the wing.

"We bought the house emotionally because we loved it, but if we couldn't have run the business from the house, there's no way we would have bought it," Sharon explains. "Lots of people have inherited their big houses," she observes, "and they're looking for ways to literally keep the roofs over their heads.

"Some of them take in people, but a lot of them, in my opinion, do it quite inefficiently. It would be great if there was some marketing course they could do to sell themselves properly and generate more income." The name of the business Sharon is involved in is called Kenny Marketing.

Sharon had already been in business with her husband, under the name of Kenny Marketing. They still run that business from Middleton Park. With Admats, the Kennys offer free beermats to various pubs, which have the premises's name on one side and an advertiser on the other, who has sponsored the cost of the mats. They will be launching Adlids later in the year: client ads on the back of Chinese and Indian takeaway lids. But with the big house came scope for big new ideas.

Because of Barney Curley's raffle, Middleton Park comes with built-in publicity. With so many bedrooms in the house, Sharon Kenny intends to facilitate weddings, meetings and other events. Already, the Westmeath branch of the Women in Business Network meets there.

She wants to turn the 16-bedroom wing into a self-contained unit, which people can rent out. The curious are already arriving at their door, asking for accommodation. "We do offer a small amount of B&B, but we will be encouraging people to stay for a week; less turnover is less work for us.

"We've had people ringing us and asking us if we're planning anything for the millennium," Sharon adds. "There's been phenomenal interest. We were going to have our own party here that night, but we've decided to take a night off and rent the whole house out to the highest bidder. We're open to offers!"