More than half of investors set to sell had undervalued the costs involved and said management had become a burden, P2P lending product Octopus Choice found.
However, half of landlords intend to keep or buy more homes but admit their investment will likely make less money in the future.
Profits depend on the region of the investment.
In the current climate, properties actually cost London landlords £1,250 a year for the first five years of holding the investment, according to Octopus.
And an average home in the capital worth £475,000 would have to be sold for £590,000 eight years later, for an investor to break even.
On the other hand, investors in Scotland and the East Midlands enjoy average annual returns of 8.8% and 8.2% respectively over an eight year period.
Sam Handfield-Jones, head of Octopus Choice, said: “Brits still have an incessant love affair with bricks and mortar – but the hassle and cost of buy-to-let is a source of growing frustration, and some landlords may find that their once reliable day-to-day income is becoming harder and harder to come by.
“But this isn’t the case across all parts of the market, with money still to be made from the right property in the right region.”