You don't have to be around the book-publishing world very long to discover that there are a whole lot of ambitious young novelists out there, most of them dreaming of becoming a full-time writer, with all the riches and fame which that status (allegedly) enjoys.
Anyone with such ambitions would do well to keep an eye on Bookangst 101. This is a blog run by Mad Max, an editor with a New York publisher. Max's latest piece, 28 April 2005, offers an autobiographical account from 'Keith', a thriller writer. (Most people who contribute to Max's blog seem to do so on an anonymous basis -- telling the truth, it seems, could prove harmful to one's interests.)
Keith's story will be familiar to anyone who has been keeping an eye on the publishing scene over the last few years. In summary, it runs as follows. Keith writes book; agent gets excited; publishers get excited; Keith gets contract; writes several more books; each is sold for a smaller advance than the previous one; each sells less well than the previous one; publisher loses interest; agent offers Keith to lots of other publishers; editors love Keith; their bean-counters look at his sales record, snigger, and say get lost; end of career, at least in the US and at least under his own name.
This is a familiar story, and one which could be told many times over; it's an everyday story of publishing folk. So my point is this: if, after years of struggle to write novels, you suddenly find yourself being offered enough money to give up the day job, then please, for everyone's sake, do not assume that you will be a writer for the rest of your life. Statistically, that is unlikely. The most probable outcome is that you will publish a couple of books, they will make little impression on the reading public, and even less impression on the bestseller lists, and then your publisher will politely decline to do any more.
The damaging effects of such a 'career' should not be underestimated. As a minimum, there will be unpleasant and possibility lasting effects on: your mental and physical health; your marital status (or girlfriend/boyfriend thing); your financial affairs; your relationships with friends; and your prospects of getting any other sort of a job.
Given that that is the case, you may care to ask yourself whether the writing business is worth all the effort. After all, to get to the point where you are likely to be offered a contract by a major publisher, you are going to have to put in a good few years of hard work -- work which will certainly distract you from your social and professional life. And, as we have seen proved time and time again, the commitment of time and effort is by no means sufficient to guarantee success.
Think carefully, is my advice. Perhaps, while you are briefly enjoying your status as a full-time writer, it might be a good idea to take evening classes in how to become a plumber.