I was wondering if I created a website on weebly.com i.e. one which had a url like yoursite.weebly.com, can I sell a site like this or must it be on a different host and be just .com?
you can definitely sell it, but first check the legal terms on weebly. not many would want a site that is under a freehosting account or sub domain.
Yes its salesable but its against the TOS of weebly. For example,you can sell many people looking for blog hosted at blogspot that have PR. So same rule apply for weebly subdomain site.