If it'll be any help (just for ideas on how to make it work; I don't mean "Copy these guys!"), there's an online tattoo commission site that has a good system that works. From the looks of it, customizing any-which-way is possible (so setting up for the share-pay idea won't be a problem).
Off the Latest Things page
Date: 2014-05-28 08:02 am (UTC)–N