THINK landlord and you think property shark, raking in money from grotty bedsits or plush apartments. What you don't think is PAYE worker struggling to keep ahead of payments on a suburban semi-d. But that is now the typical profile of an emerging class of Irish landlord: those who can meet their mortgages only by renting out some space in their newly acquired homes.

The source of the trend is rapidly escalating property prices. In Dublin, prices went up by 20 per cent last year and in cities such as Galway and Cork they are also rising rapidly. Those who have not yet found a foothold on the housing ladder find they cannot raise the finance to buy a house costing £80,000 or more on the basis of salary alone.

Building societies say more and more people are considering this option, and that lenders are happy allow for rental potential when allocating finance. "When somebody comes to us for a loan," says John Boyce, head of lending in First National Building Society, we assess is their repayment capacity and we'll take all income factors into account. Income refers not just to salary but bonuses, investments and yes, rent from a lodger or tenant.

"Lenders will never look at one factor in isolation and core income would need to account for most repayments. But if somebody wants to rent space in order to increase their loan eligibility, then yes, we would certainly allow far that."

The willingness of lending agents to allow and, according to anecdotal evidence, even encourage renting a room to meet repayments is a cause of concern to Kieran Murphy, director of Threshold. "Income from a lodger/tenant is projected income rather than real income," he says, "and very liable to fluctuate.

"What happens if the lodger moves out or cannot pay rent for some reason? To have your home secured on such a volatile source of income seems fraught with danger and Threshold would advise people to seriously consider the drawbacks of taking such a step."

The drawbacks are obvious and not just financial sharing your home with a stranger is probably not something many people would do as a matter of choice. Theresa, from Clontarf in Dublin, found it "a nightmare", with one problem tenant after another. "The first guy was a pig and no amount of asking could get him to clean up. So he got his walking papers and I then took in a young woman, who used to go out most evenings and bring back a gang from the pub and they'd stay up half the night.

"My last attempt was another girl who didn't do anything wrong, but just got on my nerves. She seemed like a nice quiet person but she was totally clingy and it got so I was dreading going home from work.

"In the end, I took an evening job in the local restaurant instead. I'm often exhausted but at least I can wind down in my own home now. I'd never do it again."

Others have been more fortunate. Michael has had two paying housemates at a time since buying his house in Leopardstown, Co Dublin, five years ago. In that time, 12 people have come and gone and he would recommend the arrangement to anybody struggling with repayments.

For 39 year old Monica, separated mother of two children aged four and six, renting a room of her four bedroom house in Sandyford, Co Dublin, to Robert, a 26 year old electronic engineer, has been "a terrific idea". Monica's mortgage had been granted on the basis of maintenance payments from her ex husband in addition to her salary, "but the maintenance dried up after about a year and I was beginning to get very anxious indeed, thinking we might have to sell, which I dreaded, as we had been through so much upheaval.

"Then one morning in the canteen, I heard a colleague talking about her brother who was looking for a place to stay in my area. Something just went click in my mind and I told her I was looking for a lodger, though I hadn't been until just that moment."

A twentysomething man in a house with a thirtysomething woman and two children doesn't sound like the typical arrangement. But both parties are more than content.

"When I first moved in with Monica, I thought of it as a temporary thing," Robert says. "We said we'd review it after three months but it's two years on now and I haven't felt the need to move. The house is just a seven minute walk from work and I get on very well with Monica. She's an easygoing person, very relaxed to be around, and great for giving good advice, especially about women." And the children? "I love kids, always have. I'm the eldest of six myself and get a great buzz out of them."

Roberta is a free agent in terms of who he brings back to the house. "Once I had a girlfriend stay with me for six weeks and Monica was totally cool about it."

Monica wasn't quite as totally cool about it as Michael thought in fact. "To tell you the truth, I was just about to tell him I 5 getting cheesed off with the situation when he announced she was going back to Australia, so I never said anything," she says. "But I know that if I had, we would have talked it through rationally; there wouldn't have been a row or anything."

The factors that work for success are a matter of common sense: make rights and responsibilities clear from the beginning, state your expectations in terms of space and privacy; establish ground rules for shared space such as the TV or music system; work out in full how all payments will be handled - bills, house, maintenance, food. "Get it in writing," is Kieran Murphy's advice to those renting in someone's home, because that way they are more likely to be defined in law as lodgers rather thank tenants, and consequently have fewer rights.

According to the law, the difference between a tenant and a lodger is "the retention of control by the owner over the premises occupied by the lodger and the lodger's lack of possession independent of the owner which distinguishes a lodger from a tenant". Kieran Murphy acknowledges this is a grey area.

FOR those with space to rent, perhaps the most practical tip comes from Michael: "Take in culchies. I have two country people with me at the moment and they disappear off home every weekend. During the week I'm out a couple of nights a week anyway: I hardly know they're there."

But for most people, in the end it comes down to personality and compatibility. Monica says "Robert has become like a younger brother to me. He'll babysit for me when I go out if he's not doing anything or keep an eye on them while I pop down to the shops. Having him share our home was the best thing I ever did."