It seems the only option for playing Left 4 Dead with my friends is to have all computers online, even though I bought the 4 pack from Valve. Is there anyway to plan a LAN game on Left 4 Dead 1?
It is possible. If you use srcds to set up a dedicated server and note the LAN IP of the computer hosting it, you can enable the developer console in-game (under Keyboard settings then advanced) press the ~ key (on foreign keyboards, it is usually whichever key is next to the 1 key) to open it and enter the command
If you're using a non-QWERTY keyboard, sometimes binding the developer console may not work. If so, you can edit the launch options and add
Not as far as I know, you can create a lobby and host a local server, but I believe you need to connect there through steam, and that would mean connecting to the internet.
You wouldn't be able to see your friends either, because online/offline status is determined on the steam servers.
You'd be in the same area so I assume that would make it so you don't have too much lag, but you can't avoid being online.