| Weiland |
Well, a Nurse, from Ultimate Equipment, costs 7 SP a day and is only a 1st level Expert...so a 1st level Expert or Commoner seems likely at 3sp. I'd probably go Commoner at that price, actually.
Now, a Nurse can get paid two or three times as much if they're 3rd-4th level...and I'd assume the same goes for other professions as well. So...you get what you pay for.
All NPC class characters have 13, 12, 11, 10, 9, 8, for stats, before Racial Modifiers (or 3 point-buy if you want to switch it up a bit).
They'd advance in class or level like any other NPC...which is to say when the GM says so (which can be done by giving them some share of xp, if you like).
Unfortunately, I'd have to develop a new method for xp gain other than combat and questing for some of these blokes. That's one of the things I don't particularly like about Path and D&D - good systems, iconic, very enjoyable, but by God all you can do to level up and improve is beat goblins in the head with a stick or save someone's cat from a tree.
Curiously, where are you drawing your source from? I've never run across the basic stats or growth for NPC characters.