Hi, and welcome to Guild Wars.
In all honesty, the leveling in general is so fast with any class and the need for money is so low, it really doesn't matter what class you start as. Warrior is still pretty good though, for ease of play.
As to what your friend's should play as... should be up to them. If one wants to play a healing monk, then you'd be set for a long time.
Only 2 other suggestions I can give ya':
1) Go to
http://gw.gamewikis.org/wiki/Main_Page for some detailed information about the game in general
2) Have fun