Content Re-writing and Writing

I have a requirement to rewrite content for my websites. This would be a long term contract and involves lot of content re-writing and new content creation work. I am talking about 60+ domains rewriting and writing content for 40+ new websites. The candidate must have previous experience in writing content for software related websites. Before starting the work, we would require some sample text written and based on the content selection would be made. Pricing has to be competitive as we are going to award content writing work for a long period. You can charge on the basis of per 500 word that you write.