It's entirely possible to retire by age 40.
Make sure you save as much of your income as
possible.
Don't spend on unneeded stuff. Be frugal
and save everywhere possible.
If you put $250.00 a month into savings you'd
have $3,000.00 per year and in 22 years when you're
40 you'll have $66,000.00 in your retirement
fund.
That's just an example. Of course more money
going into savings is better if possible.