Comical as it sounds, this is a true story. A man was running a recruitment consultancy from his rented apartment in the city centre. He complained about the roof and was busted when someone from the management company went to investigate the leak and discovered the apartment was a hub of enterprise. "The landlord immediately terminated his lease," says Enda McDonnell, a director of RF Property Management, the company involved.

While he says this kind of discovery is fairly infrequent, his company recently came across another case where a solicitor was running a practice from an apartment he purchased in the city centre, where he employed a number of staff. Apartment-based operations of this kind are most likely to happen in the city centre or close to centres of commercial or legal activity such as the IFSC or the Four Courts.

"If you buy a 400 to 500 sq ft apartment and kit it out as an office, it is cheaper than buying office space in the city centre. But it's very difficult to hide that kind of operation for long, especially if there are too many people coming and going."

Whether you rent or purchase a property, the lease states it is a single private residence or dwelling which cannot be used for commercial purposes. But is there a fine line between working at home and operating a business that violates the terms of your lease?

Recently, a vendor of an apartment in the IFSC in Dublin 1 rang The Irish Times property supplement to tell us that out of three people who viewed his apartment two wanted to use it as an office. It's unlikely anyone will complain if you are using your apartment as a satellite office or are quietly working at your PC or laptop. The line is crossed, says Carina Warner of Hooke & MacDonald, if clients are calling to the premises, if the apartment is used as an official business address on documentation or headed paper or if staff are employed to work on the property: "We have to be more careful when showing a ground floor with an entrance. As you don't have to go through a corridor or block to get to it would be easier to operate a business from it."

Couriers seen coming and going, or staff trudging up and down the stairs, are likely to alert residents to a commercial operation. Once reported, the management company should investigate the matter. If a business is in operation it will take steps to shut down the business.

"It is not practicable to turn a blind eye," says Enda McDonnell. "Commercial properties are insured at different rates to residential, so if a business is operating from an apartment and something happens, then there would be a huge question-mark over whether they would pay out. "For example, if a photocopier overheated and caused fire damage it is unlikely they would pay out for any damage caused within the apartment. And it's unlikely they won't find out what's been going on - they usually appoint an assessor for any claim over £1,000."

It is rarely a management company has to resort to legal action to evict a tenant or owner-occupier. Most people caught redhanded "see the writing on the wall", according to Kieran O'Brien, a partner in Bowler Geraghty & Co Solicitors. "However, some businesses can go undetected unless there is a stream of callers. If the property is rented, the landlord has no right to just walk in without notice."

If a tenant or owner-occupier refuses to co-operate, the landlord/management company can pursue them through the courts.

"If an apartment is rented, the management company will generally pursue the landlord who can apply for an injunction under Section 27 of the Planning Act and serve an enforcement notice or a notice to quit. If this fails, they can start ejectment proceedings in the Circuit Court. If they have to go the whole hog, they can get an ejectment order. The order is lodged with the sheriff who carries out the eviction."

If the culprit owns the apartment they are less likely to be asked to leave - but the management company can threaten to forfeit the lease if they continue trading.