Standing in the dining room of the early 1900s-era brick rowhouse, deep in the Bushwick section of Brooklyn with not a frozen yogurt shop or Starbucks to be found, Alan Dixon, an investor from Australia, struggled to tally the houses he had bought in the area over the last year.

“What, 70? 72?” he asked, raising his eyebrows in question at a group of investors, contractors and designers standing nearby. A dozen construction workers scurried around, fastening plasterboard to walls and laying tile on floors, readying the four-bedroom house that the group purchased in June for $635,000 for leasing in less than two weeks’ time for as much as $5,490 a month.

Finally, someone locates the number on a piece of paper — 70, later corrected to 71. “That sounds right. Something like that,” Mr. Dixon said with a laugh, tugging on the cuff of the pink shirt he wore under his gray suit jacket.

It’s easy to understand why it might be difficult for Mr. Dixon to keep track. In just two years, the investment fund he oversees for Australian investors and retirees has purchased more than 538 homes, townhouses and brownstones from Jersey City to Queens and Brooklyn.