The average landlord who sold their rental property in 2017 did so for nearly £87,000 more than they had paid for it - and one in seven doubled their money - according to estimates.
Average gains ranged from £253,981 in London to £23,874 in North East England, according to the research, which covered England and Wales.
The typical gain was £86,651, with landlords having owned the property for just over eight-and-a-half years on average, according to the calculations from estate agency and lettings agency Countrywide.
It found 14% of landlord sellers last year had doubled their money, rising to 28% in London.
Nearly nine in 10 (88%) landlord sellers sold their home for more than they paid for it, the research found.
Landlords selling in 2017 typically made slightly less than owner occupiers, who on average made £92,886. Countrywide said this is because owner occupiers typically stayed in their homes for longer, at nine years - a longer period for house prices to have increased.
Johnny Morris, research director at Countrywide, said: "House price growth has driven investor gains.
"Landlords selling in 2017 owned their homes for nearly nine years.
"In eight of those last nine years, house prices have risen. Even in areas where price growth has lagged behind, most landlords have made a profit from rising prices."
Here are the average landlord seller gains in 2017 according to Countrywide, with the average difference between the original purchase price and the sale price, the proportion of sellers making a profit and the proportion of sellers who saw their money doubled, according to Countrywide:
- London, £253,981, 96%, 28%
- South East, £108,073, 97%, 15%
- East £84,265, 94%, 13%
- South West, £57,249, 91%, 11%
- West Midlands, £40,381, 85%, 11%
- East Midlands, £38,776, 87%, 12%
- North West, £34,519, 80%, 12%
- Yorkshire and the Humber, £32,671, 78%, 11%
- Wales £30,938, 79%, 13%
- North East, £23,874, 75%, 9%