The National Asset Management Agency (Nama), the state body charged with buying and managing €90bn worth of toxic bank loans to property developers, has advertised for lawyers, real-estate valuers and auditors to help it cope with "at least 10,000" loans.

In a series of tenders published in advance of the formal establishment of the body next month, the agency also said the panel of estate agents which will help it to value all the impaired loans will be expected to be on call for the next four years.

The agency is looking for five estate agents to cover Connacht, five in Leinster and Dublin, five in Munster and five in Ulster. It is also looking for five firms to cover Britain and five to cover the major cities in the USA.

Finance minister Brian Lenihan has already said a quarter of the €90bn worth of impaired loans are located outside Ireland, the majority in the UK.

In its tender notice looking for the firm of auditors who will assess property valuations, Nama said the successful company will have to ensure the assessment of the property loans be "consistent within geographic regions, property sectors and across the whole property portfolio being acquired by Nama".

Lenihan has to date refused to say how much the taxpayer will be asked to pay to take over the €90bn worth of impaired loans, though it has been speculated that a discount of around 30%, or €60bn, would be applied.

However, the minister said that each of the 10,000 loans will be looked at separately, a task which is likely to take far longer than the four years specified by Nama.

Earlier this year, the head of the National Treasury Management Agency (NTMA), Dr Michael Somers, suggested the agency could do the work with no more than 50 of its own staff, though he added that he would expect to have assistance from bank employees who are already working on the impaired loans.

However, the agency has now been forced to seek external expert assistance to help it handle the volume of work, though there was no indication how much this expert assistance will cost the taxpayer.

Lenihan has already stressed that Nama will operate on a commercial basis "to ensure the best finance return for taxpayers from the management of the loans it purchases".

The stream of income from the 10,000 impaired loans and the proceeds from the sale of the underlying assets will form the basis of Nama's profits, though this assumes Nama will be able to sell on these assets at a profit on behalf of the taxpayers – an unenviable task considering the virtual collapse in commercial property prices.

However, Lenihan said if Nama ends up making a loss, the government intends to apply a levy on the banks to recoup the shortfall.