Dear Employer,
I am very keen to work with you as an editor and proofreader.
I am a native UK English speaker, and have worked on a variety of projects. Most notably, I have edited articles on topics related to natural history and conservation. I have written the content for several websites, and successful promotional materials for some small business ventures. Creative writing is my hobby, and currently I am writing a short novel. I have studied English grammar, and actually teach English to students of other languages part time.
To answer your other questions:
2) I would be very happy to produce a sample for you by editing a 450-500 word article.
3) I do not have experience using Wordpress. However, I have used various other web development platforms, mostly for small business websites. I have just been reading up on Wordpress, and I believe I could use it with no problems.
4) My price for 5000 words edited and proofread is $15.
Thank you for your consideration, I hope we can work together.
I look forward to hearing from you.
Yours faithfully,
David Mackereth