Think of it as a full-time job, because it probably will be. Responding to comments means you constantly have to check and respond timely to any messages. For content creation, you will need to thoroughly analyze what posts were popular on other similar pages and create an editorial calendar, with 1-2 fun posts but also 1 post that intends to sell daily. Just an image is not enough so you will have to think of the texts accompanying the pictures also. You'll discover best posts are usually those that require interaction, or contests, so that will take you time to prepare, get approval for, invite people to participate etc. So you should charge a monthly salary, maybe a bit less if you'll be working from home.