As an aspiring screenwriter you do not have to take into account any budget calculations for your work plan, do you?

In fact, writing itself does not cost that much. All you need is a cheap computer, preferably capable of Internet use, maybe a printer, and a bunch of papers. The only think that can be lacking is ideas, the most expensive component.

However, a screenwriter, like everybody, has got to live. Therefore, he is likely to need a job of any kind, at least before the first script is sold. And on the way to get this done, other financial aspects come into play.

One can, of course, mentally build up a whole world, like George Lukas, get famous, found a production company, get oneself a studio, and then produce his own movie all by oneself with all expenses covered by oneself. But, to be realistic, that is rather unlikely.