Cordless phone to corded phone?

My XFinity gateway is in a remote location in our home, so I'd like to buy a CAT-iq 2.0 cordless phone to connect to the gateway for my XFinity home phone service.  Does anyone know a compatible cordless phone or answering machine that has a "phone line out" so I could connect a corded phone to that cordless phone base?  Would like our children to have a corded, not cordless, phone to access.  Thanks.