Originally Posted by
Goblin_Priest
There's no rules against multiclassing into PC classes. As the joke went in the early strips, regarding Elan ditching all the education of starting as a wizard by just multiclassing into it. Rogue, barbarian, bard, cleric, and/or wizard would all be pretty good choices for a farmer, for example, or just about any professional. Any class, including the other NPC classes, would, actually.
A lvl 20 commoner is absurd. Commoner is basically the class for the untrained. An epic level commoner is basically a godly trained untrained person, who is godly good at absolutely nothing.