Free might mean that you do not have a domain for yourself. Rather you have a free sub-domain or sub directory. E.g.. I have a web store at
http://kimmieval.ecrater.com. This means that I am hosted through a free service and my URL reflects just that. Some search engines do not favour free services or sub domains when you submit your store. Bear in mind some persons have done it and have received rankings. But note that with changing search engine algorithms you might not be as lucky.