Need Someone that will be in charge of all the Social Marketing for a new brand

We are launching a new brand, and we are now in pre-launch, and we want to develop audiences in Pinterest, Instagram and Facebook before the first product is ready.
I need someone who is capable to create images to upload to Pinterest and Instagram, and to write posts on Facebook.
The job will begin part-time just for the month of pre-launch, but it will then become a full-time Social Media manager.