He can’t really do it because of his home layout until he gets gets conduit installed or the house properly wired up. The internet gateway is on a different floor and a repeater would likely be needed because of the distance. Also cat6 six cables going down split level stairs sounds like trouble. If he had a coax outlet anywhere nearby I’d suggest he look into a MoCa setup which I’ve had decent luck with in the past (better than WiFi, worse than cat6).