Last week I spent over an hour fixing someones Zencart installation for them. I was kind of suckered into doing this for free even though they themselves had broken it.
(Abridged and prices excluded.)
Customer Email: "Thank you for fixing the site last week, I'm still having problems with the plugin. Can you help me?"
Me Email: "I'm always willing to help. I can look at it but I'll need to invoice you on an hourly basis. I can also offer you training for either a full or half day rate. Alternatively here are the links to the ZenCart site and also the author of the plugin. "
Customer Email: "I don't need any training, I just need to know how to adjust the values on the plugin. I'll have a look at the Zencart forum when I have a minute."
Yeah, you do that.