On paper, they had the perfect rental application. Marion Mercier, 29, a legal scholar, and her partner, a cybersecurity engineer, wanted to move in together. They began looking in March, hoping to find a two-bedroom apartment to rent in the western Paris area, close to the RER A suburban train line, which connects both their workplaces. The couple's budget – up to €1,700 per month – was in line with the market's demands. "I thought we'd find something quickly, given our incomes," she said. However, it took them six months of intensive searching before they finally signed in September. They would be renting a two-bedroom apartment in the western Paris suburb of Rueil-Malmaison for €1,620 per month, including utilities.

"We started by responding to ads on [the housing websites] Seloger, Leboncoin, Bien'ici and PAP, but never got any replies. Then I called real estate agencies, but you could count on one hand the number that actually picked up the phone for us," Mercier said. When they did manage to get an invitation to an apartment viewing, most of the time nothing came of it: "We were told that our application was good, but that there were so many people whose applications were just as good."