How do I get started in the level design industry and how much can I make once I finally make it in? Mike

The answer to your first question is to buy a game, or many games, and start making levels for them. For example, Quake III has a level editing tool called QeRadiant. The tool is a free download. So just make some levels to learn how the tool works and search the internet for tutorials. Then design some levels on paper and then put them through the tool. Try to ask yourself every step of the way, "Would I play this level? Would other people?" After you have had much practice, try to make a set of levels for a specific type of play, ie Capture the Flag. Or make a set for each type of play available. Keep practising and try out the levels on other people. Then you can get a set of demo levels together for a resume.

Another good game to make levels for is Half-Life. The free level editing tool for this is WorldCraft.

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Make it work.
Make it fast.

"Commmmpuuuuterrrr.." --Scotty Star Trek IV:The Voyage Home

I agree with CaptainJester, a couple of months back Virgin Interactive were advertising for people skilled with UnrealED (the editor for Unreal/UT).
Working on mods is a great way to get yourself known in the respective community. The makers of the game may well look to the mod makers to fill in any spaces.

- DarkIce