WeWork is among the most valuable startups in the world, and as it approaches an IPO with a staggering valuation, some light has been shed on its beginnings.

The Real Deal published a deep dive Monday about Joel Schreiber, founder of Waterbridge Capital and WeWork's first investor. The Brooklyn-based Hasidic Jew, who does not take interview requests or allow photos of himself to be published, promised $15M to founders Adam Neumann and Miguel McKelvey in exchange for a third of the company in 2010.

McKelvey said in a podcast interview in June that the initial investment was a turning point in the eventual success of WeWork, which has become a behemoth with investments, partnerships and acquisitions, including stepping into coding academies, media companies and even an elementary school, with ambitions to take on the biggest players in office real estate.

But at around the time Schreiber promised his investment, he was missing payments on a $5M loan to Israeli entrepreneur Sall Shtrozberg, one of at least a dozen court cases involving Schreiber's failure to pay back loans and commissions or deliver on investment promises, according to TRD. Schreiber has reportedly paid only some of the $15M promised to WeWork, and one source told TRD that he owns at most 1% of the company.

Though Schreiber's Waterbridge has been part of such momentous deals as the first Apple Store in Williamsburg and the acquisition of One Court Square in Long Island City, if and when WeWork goes public, it could be the biggest windfall of his life.