Property owners and managers have a new outlet if they’re looking to get their empty apartments rented out on a long-term basis: Blueground. Blueground, which launched in the U.S. last year, is now ready to expand, thanks to $20 million in new funding. Blueground works with “prominent” landlords in the U.S. to turn apartment units into luxury-appointed rental units that are rented out to “vetted” renters for 30 days or longer.