Article writers needed-Native English speakers

I need native English speaking writers/ghostwriters with really good writing skills to write around 10 articles per month (it could eventually increase per week). I will pay $3.00 per 400-600 word articles, this could increase if articles prove to be highly reliable/great and also depend on your writing skills which must be simply good. I want keywords provided by me in private be in the article title, in the first sentence and must be used around 10 times all throughout the articles, in conclusion i want keyword density be around 2-2.5% or so, there are good softwares over there that can help you with that, we use IBP. I will pay as soon as I checked them all up, however, please do not copy articles or use plagiarism, we will use Copyscape and Plagiarism Detect for those purposes, do use correct spelling and punctuations same as correct grammar these are conditions for payment, therefore should be submitted to me once again if it's necessary until it is correct. You will not use or reproduce those articles ever again as I will be the sole owner, I can reply your emails just twice a day due to many things i have to do here, once you are chosen i want to see samples of your writings on the topic i want, that can be done in private email only via freelancer, same as payment only via freelancer