How locked am I in my first class choice?

[Isenveld]

You can have all classes and all jobs with a single character. Nothing locks you out of any job choices. You can join all of the class-related guilds. The only restriction, if I recall correctly, is that you have to reach level 10 on your first class before the Armoury (class-change) system is unlocked.

Ah, then that's easy peasy then. Thanks!