Need help fixing intermittent Wi-Fi issues

I have my mother just about convinced to let me add Ethernet to this old house, once I am working again and have the money to pay for it, so it looks like I will have an interesting project to do this summer. I am hoping she will let me add some drops inside the walls, of course, this means I will be tearing up plaster and adding a Network closet. I will be assuming all the costs, but I am willing to do that, I am developing a real hatred for WIFI.