City are set to make Mendy the world's most expensive defender at around £52million while reports on Saturday evening have revealed a swoop for Brazilian full-back Danilo is also close.
City are in the United States on their pre-season tour and will face Real Madrid in Los Angeles on Wednesday which is likely to be the ideal time for that deal to be wrapped up.
The club appear ready to continue their lavish spending on a back line that already contains Kyle Walker, who came in for an initial £45million from Tottenham this summer, and last year's £47.5million arrival John Stones.
Pep Guardiola has also drafted Portuguese goalkeeper Ederson (£35million), Douglas Luiz (£10million) and Mendy's former Monaco team-mate, Bernardo Silva, for £43million.
Should Mendy and Danilo both check into the Etihad Stadium, City's spending since their third-placed Premier League finish last season would move beyond £200million.
Since the end of the campaign, the club have allowed ageing full-backs Pablo Zabaleta, Bacary Sagna and Gael Clichy to move on, with Aleksandar Kolarov set to head to Roma in the coming days.