Mobirise is free to-download software for web building. However, if you require any feature plugins or supplemental themes, you must pay for them. Unless you want Mobirise to host your site, you'll also need to spend for hosting and a domain. In that case, you'll get a Mobirise-branded web address. You'll need to buy your domain and use a new host if you want to use it without the Mobirise branding.