Excellent native English writer needed

I am in search of a native English writer to write blog posts for my new blog. My blog is about digital cameras. I would prefer someone who has immaculate writing skills, who performs adequate research and always deliver articles on time. I prefer quality over quantity so you can set your own work load but I require a daily supply of articles. My budget is $15 per 500 words. Bid for 50 articles. The project will be extended, once the initial 50 articles are done. Finally, I require bidders to write a sample article on a relevant topic to my requirements just to judge the writing skills. Don't worry, I won't ask for samples individually, will assign a common topic for everyone so you can be sure that I am not cheating anyone. The rights to sample article will be yours and I won't use it anywhere. It is just for evaluation purpose. Thanks.