Siobhán McAleer apologises for being hoarse. It's a bright Tuesday morning in Dublin and she has spent the previous afternoon in Omagh loudly welcoming home the victorious Tyrone footballers. The triumph over Kerry seems to have revealed to her an essential truth.

"There's belief and then there's arrogance," she says. "I think belief won the day."

Entrepreneurs have to think like this. Belief gets started, but arrogance can topple them too. Although she doesn't quite come out and say it directly – and she says most things directly – McAleer probably had a helping of both qualities when she founded The Mortgage Shop in Belfast as an ambitious but somewhat desperate 24-year-old single mother in 1992. It's now a thriving business with 28 franchises in Northern Ireland and 17 in the Republic since first opening south of the border in July 2007. But life wasn't always this good.

Having joined the managerial track at Abbey National after graduating with a law degree from Manchester University, McAleer was "stopped in her tracks" when she got pregnant, her relationship broke down and she began to feel her career was being "written off" at the bank. This self-described "driven achiever" found herself heading back to tiny Dromore, to which she "never wanted to go back", in need of her family's support. A good dose of sibling rivalry helped her get things moving again in the right direction.

"I stayed with Abbey but struggled with the baby. I struggled emotionally and lost my way for maybe a year," she says. "Then when my younger sister came back from England and opened up Northern Ireland's first Specsavers franchise, I thought, 'Well, if she can do it so can I'."

As she tells it, McAleer had no big plan – "nobody dreams of becoming a mortgage broker" – but she had noticed a significant shift in customer behaviour at the Abbey branch where she was a manager: even the most loyal customers started asking about what Nationwide and Halifax were offering. Mortgage switching was about to start driving competition between the banks and McAleer saw her opening.

"At that stage there were no pure mortgage brokers in Northern Ireland. Nobody thought for a second there was any real financial advantage in looking elsewhere," she says. "It was all about just getting a mortgage, not getting a deal. Those were the days you had to save with a lender to get a loan."

McAleer knew at the time that insurance companies were looking for distribution, so she went to Legal & General, gave her pitch and walked out with a £60,000 interest-free loan to become a tied agent. Her father, a successful builder, guaranteed a lease on a premises in central Belfast. The Mortgage Shop was in business.

"I thought I was Rockefeller and naively opened a second office in Derry. Within 18 months my accountant was having a very courageous conversation with me, saying I should walk out the door and never come back. That day I learned what overtrading was."

She also learned the line between belief and arrogance.

"I remember walking out of the office and standing outside my sister's very successful Specsavers franchise and he said, 'I think you should walk away, but if anyone can turn this around I think you can, but you need an investor'."

Fresh capital arrived, fortuitously, in the form of a peace dividend. It was after the first IRA ceasefire in 1994 and investment was starting to pour into Northern Ireland. A plc offered £50,000 for the lease on her Derry shop, so she took the money and consolidated the business in Belfast. After a year-and-a-half of regaining her nerve and getting back on top of her finances, an employee opened the first franchise outlet in Andersonstown.

Since then it has been a mostly upwards trajectory for The Mortgage Shop, which grew to 28 franchises in the North as the property market took off. Eventually the lure of higher fees and the opportunity to mop up business in a bigger but fragmented market brought her attention to the Republic. Either here or Britain was the next logical step, and McAleer's "Irish blood" kept her inclined towards home and the familiar. But there were some surprises.

"There were hurdles here I did not see," she says. "To me a broker was always about getting the best deal for the client. Down here it's just about haggling and trying to get the customer more money than they'd be able to negotiate themselves, like a hustler.

"That was the biggest cultural shock. [There was] no emphasis on the best deal, no emphasis on record-keeping. Justifying the deal people have is very difficult if they're with the lender purely based on amount."

Technically, the Financial Regulator requires all brokers to be able to justify their deals in this way, but according to McAleer, this simply wasn't the case as recently as 2007. She says the regulator is tightenging this up, but when the Mortgage Shop began researching the market in early 2007, there was less evidence of strict supervision – a result, she says, of a system that leaves too much discretion to brokers and banks.

The result is a market where a handful of banks carve up the brokers between them, with customers missing out on the full spread of options unless they do all the legwork themselves.

"A broker should be able to show a spread of lenders on one A4 sheet. You can tell with one glance whether they're a good broker or not," she says. "The relationship between consumers and brokers in the Republic is damaged because a lack of professionalism. It would worry me that lenders will close ranks against brokers because of that."

She sees a bleak future for brokers who fail to raise their game, pointing out that, because of boom-time complacency, most here stopped selling mortgage protection insurance alongside mortgages, allowing a potentially strong revenue stream to slow to a trickle. In Northern Ireland, 60% of a broker's revenue comes from the insurance side, while in the Republic the typical broker is 80% weighted towards the mortgage side.

This is where McAleer senses a competitive advantage for those who join her franchise – that and cost. After some initial struggles and hard bargaining, The Mortgage Shop acquired a unified licence for all its franchisees, meaning the Financial Regulator has a single point of contact with the corporation rather than with each individual broker. At a time when compliance costs are cited by independents as a huge burden, The Mortgage Shop could prove a safe port in a recessionary storm.

"We are a leaner and meaner machine. It cuts our costs," says McAleer. "We're looking a lot more closely at protection needs. When things are difficult, people need sickness and redundancy cover, life policies."

McAleer's hope is to be the "last man standing" when the market eventually rights itself in a couple of years, when all the dead wood is cleared out of the broker market and the banks and consumers are ready to pay for a higher-quality service that delivers value and reliability. The omens from Omagh appear promising.

curriculum vitae

Siobhán McAleer

Age: 42

Career: legal adviser with Abbey National before founding The Mortgage Shop in 1992

Education: Law degree from Manchester University

Family: Married to Gerry with two children

Spare time Activities: Husband, children, food and wine, in that order