Maybe your friend would like to give his house to someone else who could use, just kidding, we don't need bigger houses what we need is less stuff.
But given a big house if you need to get WIFE to all corners of the house there are lots of different options. You could get a range extender. Every manufacture of networking equipment makes range extenders but they all kind of well they're not great None of them works really well.
A better alternative is to look for a new technology called mesh networking and each of the big networking vendors makes something or provide some hardware that will provide this service. The one I happen to like best is from a company called EERO. eero.com
Oh it's very simple to set up. There are attractive little units you can buy a set of 3 of them for somewhere around $300.00. It's not cheap but it's super easy to set up.
Netgear.com makes one called the ORBI and there are others from other vendors as well.
You find the one you like. You can do research online and you just have to hook a wire up to one of them. So your wire comes in from ISP, whatever it is from Comcast or AT&T or whatever it is and that wire goes into one of the EERO units and then the others you spread around your house to get signal to wherever you need it.
There's instructions that are provided by these manufacturers. They're simple to set up and after being out for a few years now they're very reliable. Check out mesh networking for more information about getting your WIFI signal to all areas of your large house.