FWIW I just looked up "Guest" in my dictionary (Chambers):

"A visitor received and entertained gratuitously or for payment. A person visting one's home by invitation, to stay, for a meal etc; a person paying for accommodation in a hotel etc; a person honoured with hospitality by a government, organization etc; an animal inhabiting or breeding in another's nest (zool). Not a regular member of a company etc or not regularly appearing on a programme, but taking part on a special occasion".