I don't think it'd be the wisest idea to buy a server off the bat. What are you trying to do?

You'd most likely wan't to host it at a datacenter (known as colocation). Hosting it on your home connection is too slow, and could only handle a few people.

As a webmaster myself, I suggest against getting a server if you're going to host a site. Buy one from a host for 5$ a month and save the money. Or rent a dedicated - it's a lot easier.

FreeBSD is where its at - it's powerful software. If you're new, you may wan't to aquire a licence of cPanel so you can easily manage your site without having to run SSH comman - which is a bitch.