Almost half of landlords of houses and apartments do not receive enough rent to cover the interest on their mortgages.
The finding is as a result of an academic study of survey of 493 buy-to-let investors.
It found 49% of respondents do not receive sufficient rental income to cover their interest payments but have not opted to sell their investments.
Some 44% of respondents say they can afford to absorb the loss they will incur if they sell their properties but have opted not to do so.
It also found 57% of landlords bought properties near where they lived.
The study was based the database of MortgageBrokers.ie conducted by TCD Professor Brian Lucy, Karl Deeter of Irish Mortgage Brokers and Marie Hunt of Estate Agents CBRE.