It's a great career, particularly if you are a people person. From experience it takes a little time to build up your knowledge of the market but once you've done that and you have a solid base of clients you'll find it a breeze.
My salary after just 3 years of headhunting was just shy of 75k and I would say 100k is quite easily achievable within 5-6 years if you can build the client base. Some of my banking head hunting friends earn way in excess of 150k per year.
It isn't always the most mentally challenging job in the world though so don't expect to be splitting the atom! :)