If I've told you once ...

... I've told you a thousand times. (Or at least five ...)
(See here and here and here and here)

Don't write because you hope it will make you rich.

An article in The Times (thanks to Absolute Vanilla for the link) makes the case crystal clear.
The words 'brutal' and 'reality' leap to mind.

Here's an extract for those who can't be arsed to check the link:

Last month The Times published statistics from Nielsen Bookscan, which tracks book sales nationwide, showing that, of 200,000 books on sale last year, 190,000 titles sold fewer than 3,500 copies. More devastating still, of 85,933 new books, as many as 58,325 sold an average of just 18 copies. And things aren't much better over the pond: I read recently that, of the 1.2million titles sold in the United States in 2004, only 2 per cent sold more than 5,000 copies.