Not really getting the concept but before you even consider hiring freelancer, a big question is, do you have the money to hire them? Do you know how to hire freelance developers? (Going on elance and hiring cheap developers will probably get you nowhere - I've been there). Do you also need to hire a designer and a front-end developer? Are you trying to build a team or just get the website built and be done with?

Either way, you'll need to do a realistic financial projection to see if you have the money to hire an agency or a freelancer. A good approach would be to write down all the features your website will have (hopefully not that many), draw up a simple information flow diagram, and wireframe the concept using something like balsamiq. After you get all of that done, talk to a couple of reputable agencies and see how much they'll do the work for so you have a general idea of how much it'll cost (but they usually ask for your budget first). If that doesn't work out, guesstimate how long each feature will take to complete. Multiply that by 4 and the hourly cost of the programmer (and designer and front-end engineer if you need them) and you should get a decent estimate of the cost.