Hey, took me about 2 years of training on and off, but you could realistically probably do it in 12-18 months.
Things I learned that I wish I knew sooner
Strengthen the surrounding muscles through other workouts, this includes the lower back, hip flexors, glutes, and hamstrings. Having a strong base strength here will help you once you become fatigued, as your body will kind of 'default' to the strongest remaining muscle which is what can cause pain/ injury especially in the knees..
If you are running on harder surfaces especially, get proper running shoes and some insoles as well, this will reduce foot pain and knee pain as it will soften the impact overall.
Stretch, before and after. I gave myself back spasms and lost 2-3 weeks right before my official race as a result.
I won't give dietary advice because there is plenty of advice to be found on running diets, and different people have different results..
If you are running on a treadmill, turn the incline up a percent or two to avoid 'cheating' the treadmill by hopping and avoiding actually running the amount you're supposed to (You won't do this on purpose likely, it just can happen).
I think a good general program is to have 3-4 runs per week.
One 'long run' at a moderate pace
One 'very fast run' at the hardest pace you can go, but for a rather short distance, anywhere from 3-9 miles depending on your conditioning.
One-two 'workout runs' at a little faster than moderate pace, but are not at your 'max distance'.
I'm not a professional or anything, just figured I'd give you the noobie experience for someone who dealt with the entirety of the process.