You won't. Ever. Not if your life depended on it. You'd be just as likely to become a rock star or a movie star. You will not be JK Rowling, Stephen King is untouchable (and suffered like HELL for his craft!), and Stephanie Meyer is a FLUKE. Only Dan Brown could be Dan Brown, and Jane Austin has been dead for some time now, having never made the bestseller list. You'll also never be Ayn Rand, never sell like Tolkein or CS Lewis, and your book will never become - or even be optioned for - a movie.
Further, if you're hoping to make money for your manuscript, give up now. You're writing for the wrong reasons. You're not ever going to make it big. Period.
The truth, though, is that as much as a writer might want to make it big, might hope for the success of Twilight or Harry Potter, we're lonesome, quiet souls who feel better in front of a computer screen than an audience; we don't really want that fame. And for those who do, they will be sorely disappointed.
Because no one makes it big like that. That's reality.
The flipside is, if you're writing for yourself, if you're in love with your own story and your own characters, and if you are only eager to share your work in hopes that others might feel the same way, even selling one book makes you a bestseller. One single conversation with a dear friend or an email loaded with compliments and kindness about the characters you've created can make you feel like the richest writer in the world. (Thank you, Tara and Jessica and Heather!) If you're writing because you must, you immediately become the wealthiest person in the world.
Loving your writing is like loving a person: it is its own reward. A single printed copy of your work - traditionally published, self-published, even an e-book - puts you at the top of your own bestseller list, and there is no better feeling in the world. The horrible truth about making the bestseller list is that you won't; the beautiful truth is that it just doesn't matter. Life...is...beautiful.