Suffolk County is one of the best places in the metropolitan area to invest in a rental home, according to a recent analysis by HomeUnion, an online real estate investment management firm.

Suffolk — which had an average capitalization rate of 5.3 percent, the return rate from the income generated by the property, and a median investment sales price of $340,000 at the end of last year — came in third in the New York metropolitan area, behind Middlesex and Union counties in New Jersey.

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Nassau County came in sixth place, with an average capitalization rate of 4.1 percent and a median investment home price of $439,000.

The capitalization rate is a measurement of risk, says Steve Hovland, manager of research services for HomeUnion. Investors pay more for homes in Nassau County, but they don’t see a much greater monthly return, as median rents were $2,821 in Nassau versus $2,625 in Suffolk.

“You’re going to get a lot more rent for your price in Suffolk than in Nassau County,” Hovland says. ”When investors are buying at lower cap rates, it’s going to be more of a cash flow.”

Manhattan was the worst place to invest, with a 1.9 percent capitalization rate. The median investment sales price there was $1.4 million with a median rent of $3,617.