More and more people are finding it difficult to get on the property ladder. Estate agents across the country, and particularly those with new housing schemes pitched at first-time buyers, say they are having to turn people away.

Couples turn up with deposits but no loans arranged and later find it impossible to get loans for the amounts they require.

According to Mr Tom Horkan, director of mortgage advisers MMPI in Donnybrook, Dublin, it is getting far harder to get loans, but the reason for this is not so much lender caution as prices rising faster than salaries. That said, lenders are also more rigid in applying their criteria than they were only a year or two ago, following repeated warnings from the Central Bank.

Most lenders will now advance about three times the applicant's income. So someone earning £20,000 a year can expect to get a loan of £60,000, while someone on £30,000 can expect to raise about £90,000.

Mr Horkan says some lenders, including First Active and IIB, will lend about 3.25 times the applicant's salary. For the person on £20,000, that would mean a loan of £65,000, while for the person on £30,000 the loan would rise to £97,500. That can be the difference between being able to afford a home or not.

For couples, the second income is only added on. So where both partners are earning £20,000, the total loan they could get under most lenders' guidelines would be £80,000. If the higher earner was on £30,000 and the lower on £20,000, it would mean a loan of £110,000.

Irish Permanent is an exception to this. It will approve a loan for 2.5 times the combined salary, less any debt owed. That would mean that the couple who are both on £20,000 could raise £100,000, while the couple earning £30,000 and £20,000 could get £125,000.

The Irish Permanent formula allows for a larger loan for almost all couples, according to Mr Horkan, and it is proving very popular.

But even these multiples are not completely fixed. Professional people, such as doctors, accountants or solicitors, will often be looked on more favourably, because they can generally expect salary increases far greater than most other workers. According to Mr Horkan, such professionals can often get loans of 3.5 times or even four times their salaries. This also used to be the case for IT professionals. However, lenders now look at these with far more care in the wake of the bursting dot.com bubble. Nevertheless, all higher income earners - often those on more than £50,000 - can be expected to be treated with more flexibility.

And even apart from the multiple system, lenders also operate the formula of percentage of net income. This means the bank or building society will lend an amount of money which will set the repayment at 30 to 35 per cent of your take-home salary.

For example, if your take-home pay is £1,500, the lender may decide you can afford a repayment of £450 a month, or up to £600, and will lend based on that. That would mean a loan of around £100,000, if interest rates were 5.25 per cent.

Many lenders use this system in conjunction with multiples, but AIB uses it most of the time. Depending on how strictly it is interpreted, it can mean smaller loans than a system based on three times the applicant's salary.

Lenders will usually subtract any repayments you make on credit cards, store cards, car loans or other borrowings before working out your maximum repayment. They will then often assume that interest rates are higher than they are to make sure you could cope if rates did rise; then they will assume payments to house and life insurances, and only then will they apply the 35 per cent rule. The result can often be a small loan, particularly if you already have borrowings.

According to Mr Horkan, if this happens it is worth trying to prove your ability to repay. For example, if, as a couple, you are paying rent of £850 a month and saving £500 or paying off a few loans, then that is proof that you could meet repayments of £1,300. That would be enough for a £150,000 loan. It is possible, he says, to get up to four times your salary based on your ability to repay.