The Community Edition of Magento is free and open-sourced, but as has been pointed out in this thread, there isn't any official support.
You can find licensed developers to help you out, and there are great forums and message boards with a lot of helpful information. But you're definitely going to want to look into all the functionalities that you'll want to be baking into your site; the more you add to Magento, the more complicated things can get, from what I've heard.
Worth looking into might be a couple of other hosted shopping cart platforms: 3dCart and Bigcommerce are two really popular out-of-the-box options. They're paid and proprietary, but I've seen newer sellers create really nice-looking (and responsive, to boot!) storefronts using these platforms, and without a lot of coding or design experience at all.
Hope this helps!