I started when I was 14.
A lot of time.
But the most important thing is time and practice.
You won't learn anything if you don't repeat it over and over.
Repetition = perfection.
In the beginning, just get to know all your chords.
Then after that work on your on timing and finger speed.
Do a lot of research even on the most little things.
Theres a lot of websites out there to.
Learn how to play your favorite songs...helps you stay motivated.
Like I said, I use to play but stopped. It was just a high school thing.
But being able guitar is always a plus, people give you a lot of respect when they find out you could play...its always good to know how to play an instrument.