You need 25 times what you spend in a year. Spend $3,000 a month and your number is $900,000; spend $2,000 and it's $600,000. It's the 4% rule turned around: take 4% of 25 times your spending and you get exactly your spending.
Time to FI is in the app
The 4% rule, tested on 59 start years.
Ten years of waiting costs $651,000.
In year 11, your money starts out-earning you.