articles needed

I quality articles written. All total 250 articles to be written in 5 different catagories. So first slot comes with 50 articles. I need good quality articles with good english (no grammatical error, spelling error, plagiarism) and should be SEO friendly with keyword density. If you are not familiar with this please don't bother bidding. Please keep in mind that this will be ongoing project and more 160 articles to follow up. All articles should be of keyword strength 400-500 words and should pass copyspace. The selected bidder will get a sample article and should follow the format in the sample article. You should be able to submit the articles within deadline. So, bid accordingly as my budget is tight and will not respond to those bid which don't make any senses. I will escrow the money upon selecting the bidder and will release the money after checking all the articles.