Small-time landlords are leaving the property market and being replaced by cuckoo funds snapping up blocks of housing units to rent.
New figures also show an overall rise in the sales of homes in the summer period, buoyed by first-time buyers.
Experts said Brexit uncertainty was not yet depressing purchasing activity.
Figures from the Property Price Registers show a marked decline in small investors buying properties to rent. There were 3,156 of these small-scale cash buyers in the first half of this year. This was down 14pc on the year, which was its weakest in five years.
The figures complied by Davy Stockbrokers also show fewer small investors taking out buy-to-let mortgages.
"Small buy-to-let investors are leaving the market," Davy economist Conall Mac Coille wrote in a research note.
Small players in the rental sector are being replaced by so-called cuckoo funds, big investors who are displacing first-time and other buyers of individual units. The funds tend to buy in bulk.
There was a rise of almost 15pc in the number of housing units bought by funds and State-supported housing bodies in the first half of the year.
A total of 4,300 units were bought by what are classified as non-household buyers. This consists of funds, large rental companies, housing associations and local authorities.
The high prices funds are prepared to pay for housing units has been illustrated by the plans by two funds to sell 382 units in two recently completed schemes in Dún Laoghaire and Leopardstown in Dublin.
Tristan Capital Partners and its partner SW3 Capital are expected to sell the units for more than €200m.
This is €212,500 more than the average sale price of units across the country in the first half of the year.
Mr Mac Coille said rent controls were behind what he called the "exodus" of small investors from the rental market.
"Clearly, rent controls are persuading many small investors to shy away from the market."
There were 35,900 residential property transactions so far this year.
This amounted to €11bn, or €307,500 on average.
Mr Mac Coille said: "The housing market has remained buoyant through the summer - transaction volumes were up 4pc through July and August."
First-time-buyer activity was up 7pc in the first half of the year, defying claims that stretched affordability was pushing them out of the market, Mr Mac Coille said.