Simply...how much bandwidth will I use when running a full node at home, without mining?
Bandwidth utilization greatly depends upon whether or not inbound ports are opened up or not.
On a fast 10gbit+ VPS with inbound ports opened up, I see 280 GB inbound and 250 GB outbound used.
On a residential connection with 8 outbound connections and zero inbound, I see less than 10GB inbound / outbound used in 30 days.
You can set this when you start the daemon I believe:
monerod --help and scrolling down shows you there are these options:
So to limit your bandwidth you could type:
monerod --limit-rate 100 to limit up and downstream activity to 100kB/s each way. Or you can set them individually as shown.