Most writers I know write because they have to.
I am no exception.
There are, however, several reasons why we feel we have to write. Some have this urge inside them, stories and characters banging on your skull and internal organs to be let out. Others feel pressed to make money. Many of us, I think, have a bit of both.
To me, writing for money only used to feel like it was "less" than inspired (or urged) writing. But it doesn't have to be. If what you're writing gives something to the reader and you get something out of it as well, that's really a win-win situation.
In my younger years I felt that if you didn't know all the rules of writing, you really shouldn't try to sell others your work. While being the best you can be is what you should do, it is my belief that you can write enjoyable, good stories (or poetry, or non-fiction for that matter) without knowing all the rules.
I'm a user of English as a second language myself, and if I had waited to write until I knew every rule of the English language, I would still not have written anything. Hereby not said you shouldn't make use of beta readers/editors!You should. Beta readers and editors are our friends! In order for our work to be the best it can be, we need someone else's critical eyes to check it for us. We are often so focused on the writing itself that we might not see grammar errors, inconsistencies, telling instead of showing and other important things.
When it comes to writing for an audience, there are so many other things that come into the mix. In the time of self-publishing, many of us feel that we can't afford paying anyone else for helping us with these things - editing, like I mentioned (including getting the book optimized for Kindle if you want to go that route), promotion, cover design... While we are told never to judge a book by its cover, many of us do. If you're not too savvy when it comes to cover design, at least look at other book covers and see what you like before designing your own. If you can't make a cover you like yourself, ask someone to help you.
Once you decide to let your "baby" (in most cases, a book) go, it's in the hands of the audience. What your book looks like, both when it comes to cover, layout and its content, will point back at you. As the author, you're responsible for it. So do something you will be proud of!
That said, don't lose your passion (be it from the urge to tell a story or for making money) for writing! Keep at it, because you will get better with practice. You will learn from your mistakes. And if you take it seriously, you will hopefully get the enjoyment you deserve out of it.
Here's a book on writing that taught me a lot (so does reading his fiction books). I hope you'll enjoy it as much as I do!
On Writing by Stephen King (Kindle version). The paperback version is available here.