SEO Marketing

I am looking to start off a monthly contract with a SEO developer.

I am looking for a SEO expert to complete some routine tasks on a domain for a fixed contract. If the person si successful and works out we have at the moment 4 more contracts available (similar).

I would like the person to be able to do at least the following tasks
+ On page Optimisation
+ Off page optimisation
+ Submit sites t directories
+ Write articles
+ Social media posts

I suggest the activity to maintain and improve page position should be for 15 pages with 15 keywords
write and submit 5 articles a month
write 20 face book posts
write 150 twitter posts
Check the on page keywords optimisation monthly
Please suggest anything else