My artist is a one-way referral. We charge flat fees so he gets a percentage on every project. I supply all the info, the content, etc ... he does the graphics, typography ... I supply comments/changes .... he sends me a "package" which is all the images (cut), a document outlining all the styles and layouts, and the original files (.psd). I put the whole thing together in css/xhtml/php. He does final walkthroughs with me to know if it meets his "vision". And sometimes I have to ask for thing that weren`t working right ... missing button, content not flowing, whatever the case. Print work, erase the programming part - he sends the high-res file to the printer. We don`t have a lot of overlap - he won`t touch a line of code and I don`t know a lot about typography. So I hope that helps ... your best partnerships are going to be people who you don`t overlap with. My artist doesn`t bring in his own work, and I certainly avoid opening photoshop at all costs. If you have a background in advertising / marketing, you might do well with a "pure programmer" ... a php-coding geek type.
There ya go....the "no overlap." Remember an old, wise saying: Delegate to your weaknesses.
Something like that.
You`re also more valuable that way. Like if budget is tight on a project and you`re a contractor that does what I do, I can cut you out and do it myself.
But there`s no way I`m going to create that kind of artwork to the level of perfection that I want. So I have him.