(BLOOMBERG) - Condo sales are surging in New York City. But fewer of those buyers are tapping a once-popular investment strategy: leasing out units for income. The idea fell out of favour as rents dropped during the pandemic amid a mounting pile of apartment vacancies. Of all New York City condo units purchased last year, just 2.7 per cent were listed for rent within six months of closing, according to data compiled by StreetEasy. In 2017, the share was a record 11 per cent. "It's a strategy that has a lot of risk right now," said Ms Nancy Wu, an economist at StreetEasy. "Renting it out is very notably not-profitable because of how much rents have been dropping." Landlords have struggled to keep units filled since the pandemic shuttered offices and sent New Yorkers scurrying to the suburbs for more work-at-home space. Owners spent the past year discounting rents and upping incentives like free months to draw in tenants. Still, the number of empty units on the market has been discouragingly high. In June, despite a 38 per cent drop from the previous month, there were 11,853 available apartments in Manhattan alone. "No investor wants to go up against a landlord who has a hundred or 2...