Your hosting company should provide you an option to have a site builder as a part of your monthly service fee, or as something you can add on to your monthly service fee.

With sites like myfamily.com, they are hosting the site for you. When you pay someone else to host it, you get more creativity and also the ability to have site builder. I currently host my family site through catalog.com, which now goes under webhero. Our yearly hosting and domain charges are only 60 dollars a year, but I know it's pretty low because of how long we've had the account. I don't think it's much more expensive now though.