You could post a project on Elance, RentACoder, or Guru and mention the joint venture possibility there. However to use these boards you're going to have to pay something to the developer for the project ... I'd suggest posting a basic project to get the site framework done (look & feel), and follow up projects for additional pieces of functionality (e.g., a project to add e-commerce, a project to add flash and media, a project for
SEO, etc.). You can post a private project for a specific developer on these boards, so you can do "add on" projects with a specific developer. The nice thing about website design is, you can break it into a series of discrete projects and post the projects when you have the money for them. Be aware that at least two of these boards require you to escrow the money for a project before the developer begins work on it.
How to find someone who'll do a good job? Hire someone who has at least five projects under his/her belt, and who has a good rating on the board.
Vasily