I listened to the american writer, Elizabeth Berg, being interviewed yesterday and she said she had only been a nurse before she decided to try her hand at writing. She started writing essays as she claims it the easiest way to get published (might be in the US) - is it over here?
And issi, the book I mentioned earlier says that the biggest non-fiction 'rule' you should aim to break is the one that says 'write what you know'. Learn to discover ideas (even recycle ideas from other people) and research them - expertise not needed, just an ability to gather a few facts and write them up in an interesting way...Ok, that might be a bit simplistic but you get my meaning...