Investment real estate sales in New York have unearthed a new trend; the acquisition of small walk-up buildings throughout Manhattan.

Though previously considered relatively low-end and generally unpopular, more than 70 walk-ups were sold in Manhattan in this year’s second quarter alone. Three years ago, that figure barely passed 30. In addition, these apartment sales made almost $640 million in the first half of 2012, while 2009 saw only $210 revenue from walk-ups.

The Benchmark Real Estate Group is an example of a firm who recently took interest in the strategy, purchasing a 22-unit walk-up building at Sullivan St. in Soho. The building is now selling for $12.5 million though it was acquired for a mere $6 million.

“When we bought it, the rent rolls were about $300,000, but after renovating the apartments and pushing up rents, it is now generating $1 million,” explained a company co-founder, Jordan D. Vogel.