HTML is fun and CSS makes sure it stays fun. If you're making just a few web pages, you can skip CSS if it sounds too complicated and code the format and lay-out with the HTML itself. But when you make a site with 50 pages w/o CSS, the fun stops when it comes to updating or changing the lay-out and theme of that site. It becomes a chore. Imagine going through the code of every page just to change the color or image of your site's background.
See thats the thing with me, I'm not trying to really build a huge website like that because the updating is ugly. It's crucial and a pain I guess thats where CSS comes into play.
In that case, you can do away with CSS at the moment. Simply follow the clean principle of XHTML (no open tags, etc.). 5-10 pages wouldn't be that hard to update by hand. What's important is you enjoy what you're doing and you set-up a website. Once you get the hang of everything, the idea of learning CSS will come naturally.
What does building a website in 5 minutes do for you business? Well I guess it all depends on what you are trying to do exactly, right? that would mostly be pertaining to a newsletter or a splash page right?