WHMCS is a billing module and domains can be purchased directly from whmcs. Need a auto provision whmcs module, which can automatically setup a sitecake website when a user purchases a domain from whmcs.
so user purchases a domain and webhosting from whmcs, an HTML site is automatically created based on a predefined template. Now the user can access his site www.abc.com and when he access www.abc.com/sitecake.php he can edit all the contents.