I'm a freelance writer, and rates do depend on what type of work it is. Per word rate applies mostly to general interest, trade magazines and newspapers. $1 a word is pretty solid. Definitely go high rather than seeming like a good guy who works for cheap. Sometimes for advertising and corporate, a flat fee is negotiated, and you should be charging approx. $30/hr, depending on how much work it is (if there's a lot of research for example, a flat fee may be a better idea). Some high-end corporate technical writers charge double that. If you have any questions reach my off list at adam@adamelliottsegal.com