A Facebook page is better than nothing. It's a great first step. If you've made it that far, I applaud your efforts. If you haven't, see my post, Facebook Pages for Business 101, to get started. A Facebook page is just a starting point to get your business online.
Why should you bother having a website, when Facebook is free and it's so easy to set up? For one, Facebook controls your content and how your posts are displayed. For more reading on the legality of who owns the content you post to Facebook, this article, Who Legally Owns Your Facebook Posts, is a great primer.
In order to get your posts in front of people, you'll need to cultivate an audience of people who like your page. Unless you are a social media guru or an extremely popular business with a large existing customer base, this takes time. Your alternative is to pay Facebook for exposure. Lastly, keep in mind, not everyone uses Facebook! (Yes, I know, nearly 99.99% of people you know do.)
Having a website is critical to presenting a professional image to your customers. My previous post on why you need a professional email address talks more about this idea. It's easy to set up a basic site. There are many options, but don't feel overwhelmed. In my next several posts, I'm going to outline options that are easy to use and outline the basic pages you should have. All you need is a domain name, or URL, and a website builder. It's not hard and it won't hurt! I promise!