The buy-to-let market is too expensive for the average investor, according to the Royal Institution of Chartered Surveyors (RICS).
Buy-to-let has become increasingly popular in the last decade
It says rising interest rates and demands for higher deposits have priced out all but the wealthy.
Prospective buyers must now find 30% of a property's value, up from 8% in 2002.
The warning comes as potential landlords are told they should not see residential property as a way of "getting rich quick."
Borrowers have faced five interest rates rises since August 2006. RICS says they are now also being asked to produce a 30% deposit, costing an average of £65,600.
That has shot up since 2002, when a 8% deposit was common, an average of £10,100.
In addition, many lenders now require that the rent on any prospective buy-to-let property equates to more than 125% of the monthly mortgage payment.
This has been difficult to achieve in parts of the country where rents have been falling.
"It takes more capital than ever to set up a buy-to-let investment," said David Stubbs, RICS senior economist.
"Would-be investors who have missed out on the impressive returns of previous years are now finding the hurdles to property investment are higher than they imagined," he added.
But he believes existing landlords will be able to use the equity in their current properties to fund their next purchases.
Buy-to-let has grown sharply in recent years. In 1996, when specialist landlord mortgages were launched, only 20,000 were taken out.
By June 2007, there were 940,000 outstanding buy-to-let loans, worth £108bn.
But toughening economic conditions, and fears about an oversupply of newly-built flats in some areas, prompted the National Landlords Association (NLA) to urge caution to new investors.
"Residential property investment is not a means of getting rich quick," said NLA chairman David Salusbury.
"It is unclear whether house prices will rise or fall over the next 12 months, and those who are buying a property to let as someone's home need to have a medium or long-term perspective."
He says potential landlords must do their homework and check that the sums add up before committing to any property.
They should also make sure they understand their legal obligations.
Just under a quarter of NLA members surveyed said they intended to expand their property portfolio over the next five years.
With the number of households expected to continue to grow, NLA chairman David Salusbury insisted the prospects for the private rental sector remained strong.