Advice On How To Write And Sell Said Writing

The Poor Poet 
by
Carl Spitzweg (1839)

I am currently reading short stories that have won past Writers of the Future contests. Interspersed with the short stories are essays by famous writers with some advice to budding writers like myself.

One such section that I found in Volume XXII I found rather interesting. It is an epistolary passage, with letters exchange between writers and L. Ron Hubbard. One such writer, a certain J. Higgins, had asked Hubbard what his trick was to making a living out of writing (so many ings!). Here is the answer Hubbard crafted:

Dear Higgins,

   It isn't a question of how I started to write, it's a question of why.
   There's a world of difference there. I take it that you have a job, otherwise you wouldn't eat and if you don't eat, you don't last long.
   We assume, therefore, that you are eating. That is bad, very bad. No man who wants to start writing should be able to eat regularly. Steaks and potatoes get him out of trim.
   When a man starts to write, his mental attitude should be one of anguish. He has to sell something because he has to pay the grocery bill.
   My advice to you is simple. If you have the idea that you can write salable stuff, go off someplace and get short of money. You'll write it all right, and what's more, you'll sell it.
   Witness the case of a lady I know in New York. She was plugging at writing for some fifteen years without selling a line. She left the Big Town with her husband. In the Pacific Northwest her husband died and left her stranded.
   She went to work in a lumber mill and wrote a book about it and sold it first crack out. She worked as a waitress and wrote a book about that and sold it.
   Having succeeded with two books, she went back to the Big Town and got herself a job in the library until the returns came in. She wrote all the time after that but she was eating. In sawmill and hash house she wasn't living comfortably. She needed the extra.
   She hasn't sold a line since.
   The poet in a garret is not a bad example, after all. Personally, I write to pay my bills.
Jack London, I am told, plastered his bills over his writing desk and every time he wanted to get up or go arty he glanced at them and went right on grinding it out.
   I think if I inherited one million tomorrow, my stuff would go esoteric or otherwise blah.
   I started to write because I had come back from the West Indies where I had been hunting gold and discovered that we had a depression going on up here. Dead broke and with a newly acquired wife I had to start eating right away.
   I started writing a story a day for six weeks. I wrote that story in the afternoon and evening. I read the mag I was to make the next day before I went to bed. I plotted the yarn in my sleep, rose and wrote it, read another mag all the way through, went to bed...
   Out of that month and a half of work I have sold fiction to the sum of nine hundred dollars. At the end of the six weeks I received checks amounting to three hundred and two dollars and fifty cents.
   Unable to stand prosperity, I left for California. I got broke there, wrote for a month without stopping to breathe, sold eleven hundred dollars' worth.
   Nothing like necessity to take all this nonsense about how you ought to reform editors right out of your head.
   (...) remember this: You are the writer. You have to learn your own game. (...)

  Best regards,

L. Ron Hubbard

New York City

My interpretation is that you need to be so into your writing, there's nothing else for you but to write. Now I'm not advocating you should forgo food--that's a very unhealthy choice there. But it's true that, if you know there's no other choice for you but to write (or if you have a looming deadline), you'll be more likely to do so, and be a lot more prolific than otherwise. 

I also surmise from his letter that to also be able to sell such writing, it needs to please the editors (or, as I see it in this Age of Self-Publishing, the readers), which means you may have to forgo those eccentric, artistic bits of writing for a while, and yes, make your story more "commercial" in a sense.