Someone on DeviantArt asked me if I did commissions. I hadn't really thought about it.

Does anyone here have experience with that? How do I decide what I should charge? How do digital-only commissions work, anyway?

There is a DAZ artist guild group at Deviantart. They might be able to give you some insight.
http://daz-artists-guild.deviantart.com/

Do not be afraid commissions. Beware if they are not.