As far as wiring goes...
It all depends on where you live, and when your house was built. I live in Fenney and there is traditional cable TV coax from the low voltage box in the garage to every room of the house. The house was also wired for traditional (POTS) wired telephone service. When I inspected the cables (also in the low voltage cabinet) I found that the telephone wiring was CAT 5e. This can be used for Ethernet. I disconnected the wires in the low voltage box and put Ethernet connectors on the ends of the wires. The I did the same in the rooms that had the telephone jacks that I wanted to use for Ethernet. I also had to change the face plates on the wall.
Having said all of this, you CAN use the unused cable lines for Ethernet with MoCA adapters. This is a more expensive solution but you don't have to mess with putting the Ethernet adapters on the wires nor change the wall plates.
https://www.amazon.com/TRENDnet-Ethe...18&sr=8-6&th=1