WeWork, a real estate firm that leases shared office space, officially set in motion the process of becoming a publicly traded company by filing a financial prospectus with regulators on Wednesday.

The offering by the company, which is led by a brash Israeli entrepreneur and backed by money from Saudi Arabia, will be a major test of investors’ appetite for fast-growing but unprofitable start-ups. Similar moves this year by the ride-hailing rivals Uber and Lyft proved to be disappointments.

WeWork, which is valued at nearly $50 billion as a private company, faces sharp questions about its business model. It lost more than $1.6 billion last year on just $1.8 billion in revenue, according to the prospectus. By comparison, Uber lost $1.8 billion last year on revenue of $11.3 billion. WeWork’s losses accelerated in the first half of 2019, although its revenue more than doubled, the filing shows.

The company’s core business is simple: It takes out long-term leases on commercial real estate, spiffs up the spaces with amenities like fashionable furniture and free beer, and then rents out individual offices and larger suites to other companies.