Looking for a long-term freelancer.

I am looking for a long-term freelancer for the blogs of our company.
Each month we will need 15 to 20 new SEO articles about different topics. Please find the summary of the basic requirements for the writers.
1. Native English spekaer is preferred.
2. Willing to research on different topics and provide interesting content to readers.
3. Be creative with the guideline provided.
4. Provide error-free article.
5. Writing should pass copyscape or other plagiarism checker.

Note: The price listed here is for three articles. For long-term cooperation, the price will be 20USD per 1500 words.
Check the attached file for the detailed version of article writing requirements.