Cost Of Living In Mexico (Mexico City)

Hi, I appreciate that this question has been asked so many times, but, what is the minimum monthly income needed to live in Mexico, ????

I have chosen no specific city, I am just considering re-locating from the Philippines.

Any advice would be very much appreciated, thanks in advance.

ps I am single, no kids, 40 years old, live on a British Army Pension, so not looking for the Ritz.