Real estate in Mott Haven, once a notoriously crime-ridden neighborhood in the South Bronx, is getting hotter by the week.

Developer Lightstone just scooped up a pair of properties along the Harlem River for $59 million, or $125 a foot, with plans to build a new apartment complex on the sites, sources told The Post.

That’s $45 a foot more than the same developer paid for a 99-year lease on a nearby parcel just six weeks ago.

Lightstone President Mitchell Hochberg told the Commercial Observer on Wednesday that the firm plans to build about 2,000 units of housing on the two sites, which will include 70 percent market rate units, 30 percent affordable, a retail component and parking.

Construction is slated to start next year and finish in 2022.

Lightstone beat out a dozen other suitors eager to gain a foothold in the Bronx’s residential renaissance by leaping from offer to all-cash closing in just one week.

To push the interest and pricing, two property owners at 355 and 399 Exterior St. agreed to offer their sites as a package which was marketed by Jason Meister, Marion Jones and Christopher Gillis of Ackman-Ziff.

“There was no contract and there was no due diligence, it was a straight, fast, cash close,” said Meister of Ackman-Ziff which closed on Tuesday night.

The purchase ensures that Lightstone controls most of the area along Exterior Street between the 138th St./Madison Ave. and 145th St. bridges with the ability to construct a 1.464 million-square-foot project on either side of a future city park.

An already underway 1,300-unit residential project being developed by Brookfield straddles the 138th Street Bridge and sold last year for $165 million, or $145 per foot.

Developers are swarming the neighborhood that was rezoned by the city in 2009, giving it the boost it needed to become the next hot residential area as it is just a subway ride or fast walk over the bridges to Manhattan.

“I’ve always felt the South Bronx was a very important place for development and [Lightstone] is making a really smart choice,” says Keith Rubenstein of Somerset Partners who assembled and sold Brookfield their site and owns numerous properties in the area.