A cross bike will have a slightly more relaxed geometry than most pure road bikes, but still has the drop handlebars to get you in a more aero position. They also have wider tires, greater frame clearance for mud and usually different cable routing, all so the bike performs better in the muddy conditions of CX racing. Hybrid bikes are generally more relaxed still, with flat handlebars that place you in a very upright seated position. If you plan to ride mostly paved roads with a little bit of light dirt or fine gravel thrown in, a cross bike sounds like a good fit for you. Look for a used bike that's a few years old from the big manufacturers (Trek, specialized, giant, etc.) and you should be able to find something for around $500 that will hold up better than if you get a new bike for the same price.