There are generally monthly fees associated with hosting a web site, however, when you agree to host a site on a yearly basis we can get discounted prices at our hosting service.  When we save, you save... 

As for our part, we only charge you when we do work for you.  So, if after the initial setup, you are happy with your site for 3 years (and you have paid for your domain name and hosting service for that long) there are no further charges from us. 

However, IF your site becomes popular and you exceed your space/usage quota for your hosting agreement, we will need to work with you to "upgrade" your service (at additional cost to you) to make sure your site is available at all times.  It is possible to do a "one time" increase if the extra traffic is from an unusual event, or upgrade the hosting service to a higher level if you think the traffic will continue to grow.