Zillow, the real estate search and advertising platform, has gotten into the house-flipping business in a big way. That means the company earned about 41.5% of its revenue from selling homes in the three months ending June 30, according to its most recent earnings report.

Zillow made $599.6 million in revenue last quarter, $248.9 million of which came from its Homes segment, which refers to the "buying and selling of homes directly

through the Zillow Offers service," which it kicked off in 2018.

Zillow is now buying thousands of properties, investing in minor repairs, and then selling them — essentially flipping houses — in 15 markets around the country, with plans to be in 26 markets by mid-2020. It collects a fee from the seller with each of these transactions. The company sold 786 homes and bought 1,535 homes from April to June.

This is not yet a profitable business for Zillow. Its Homes segment lost $71.1 million last quarter. But the company plans to eventually make money from the program by attracting more mortgage customers (it acquired a small mortgage company in November) through these sales, and also selling referrals to real estate agents as more homeowners express interest in selling their homes to Zillow. The company reported receiving about 70,000 seller inquiries last quarter.

It's a major change from Zillow's original business of real estate search and marketing, and it signals a dramatic shift in house flipping from small real estate investors to institutional investors. Other companies including Opendoor, Offerpad, Redfin, and Knock are also expanding the so-called instant buyer, or "iBuyer," market. Zillow plans to buy 5,000 homes per month by 2022.