It's a good idea to review your website periodically and make changes to it. By the way, if you are concerned that your website may have the same theme as a number of other sites, your Web designer can create one tailored to your requirements. That's somewhat like asking how much a car costs. Registering a domain name is going to be the least expensive item. The cost for Web hosting varies dramatically.
Most places charge more for a business website than for a personal one.
Some adjust their charges based on the amount of traffic your site generates. In general, the more pages you have the more it will cost but this is usually broken down into groups or plateaus. Publicizing your site is the most important thing you can do to maximize its effectiveness. Sometimes Web hosting services will offer a free or nearly free service where your site is submitted to various search engines. This is not a recommended choice because your exposure is minimal.