The most lucrative year I ever had as a writer, I only made $17,000 before taxes.
This year I will probably make $12,000. (And that includes the money I bring in from being a Writing Coach/Editor.)
The key is to find a part time day job that you love and stick with that -- between that and writing you can make a good living without the awful pressure the comes from having to pay all your bills with your pen. (A good day job can give you good material to write about too.)