I general charge my clients by the hour. I'm a Graphic Artist/web designer/online marketing consultant.
One of my clients is having me set up a blog for him and then he wants me to research and ghost write blog posts for him. It's a topic I know next to nothing about, which he knows, but he trusts me to do the research and ask him if I am not sure about something. He will also approve all posts before they are posted to the blog. To begin with it will be on a monthly basis as we are also sourcing guest bloggers in his field.
But I can't figure out if I should charge him a flat rate per post or also charge him hourly, as I do for the design/online marketing work I am doing for him. If there's lots of info for the topic it may take me less than an hour one month or it could take days another month!
Any opinions? Do you ghost write? How do you charge?