So you want to write? You feel you have a story to tell but aren't sure if you have what it takes. I am no expert so I might be the wrong person to hand out free advice, but I'm going to share a few things so maybe you will avoid some of the problems I've had to deal with in the past.
First, and I've touched on this before but I feel it needs repeating, you are going to be terrible when you start out. Whatever you write will be nothing like what's in your head and it might even make you cringe a little to even remember years down the road.
Secondly you will get better as you keep writing. Even if you feel you can't and won't, write for a few months. Go back to the thing you started on and compare it to what you've got at the end of that little voyage of self-improvement. You got better! You might not understand how since you're probably beating on the proverbial walls of the internet demanding for somebody, anybody, to look at this wonderful thing you wrote and tell you how to make it better. Maybe you didn't and you feel it's too embarrassing to share.
Yet it's still better than that First Thing.
How do I know this? We're getting to my third point. I'm exactly where you're sitting doubting if anything I've got will catch someone's attention without having to mug them and demand, at metaphorical (hopefully, otherwise this will get very messy for you later) gunpoint, they read this thing and tell you how to make it better.
As varied and as wide as the Internet is finding an audience is difficult. Finding one that will sit and give you feedback is next to impossible. You can't rely on outside people to help proof and guide. You might get lucky and have a friend or two that will be interested for a little while, but nobody will be as interested in the thing you're working on as you until it is finished.
Lastly there is editing. Maybe you like the idea of going over the same material again and again re-jiggling this and that to better sentence structure and correct those oddball but inevitable punctuation errors. That's never been me and I hate editing worse than almost anything that isn't listed as crimes against humanity. The last book I wrote was a collection of short stories, which was actually fun to write. Took me all said and done, with breaks here and there, about three months to write everything. Granted this wasn't three solid months since some of the material was old and I'd left sitting for awhile but if I had to sit and give a time frame I'd say three months for the first draft.
Editing that same chunk of words took at least six months, possibly as long as nine and I can't be sure because I didn't keep very god track and it wasn't a single solid 'I'm going to sit down and do this thing' process. It was more 'Oh I'm going to put this up on Smashwords let's give it another go through.' followed by swearing and cursing and me having to start picking everything around for what felt like the eight millionth time.
You'll cry, curse, spit, howl, rage, and then cry some more before it's over and the whole time wonder if it's worth the trouble because at best, and this is being optimistic, you have to write and have published a minimum of four moderately successful books per year to make the equivalent of minimum wage. Oh it can be done and often has, plus you have the outliers like Jim Butcher, or Janet Evanovich that can make enough to live fairly comfortably with maybe one a year.
For me though writing is less about money and more an outlet. I have not yet found my audience, and I'm crawling out of the sinkhole of being upset that The Internet isn't giving me everything I want so I can be a better storyteller on a silver platter, but writing is something I do and probably will always do in some form or fashion.
Nobody ever said this would be easy. Nothing worth doing ever is.