PCs as Mentors

[Wolfgang Hype]

I'm running a Pathfinder game and one of my PCs wants to take on a student. However I'm not really sure how one would handle this. I don't really want to say "Alright, you have some guy following you around doing what you say" for free, but I'm not really sure that the Leadership feat would fit the bill.

My current thought is to roll a percentile to determine if he can find someone to teach, and having the target be below half his level times ten (he's 4th level, so a 20 or lower) and then throw in some other modifiers (he's a witch, so people might be wary of that but he's already started to make a name for himself). After that, I'm thinking of restricting his student's level to half of his current level and forcing him to pay half of his student's wealth per level (500gp once the student reaches level 2, 1k for level 3, 1.5k for level 4 and so on).

Anyway, that's my idea on how to handle it. Any comments or suggestions?

[Coidzor]

How much do you hate D&D 3.5? They already have some published feats/mechanics in, IIRC, their DMG II.

[FMArthur]

First of all, I just want to say that I don't think 4th level is high enough to be considered a mentor as an adventurer, but here's my suggestion regardless:

See where he wants to go with it;
If it's his intent to eventually make the apprentice his main character, like setting up a heroic sacrifice moment for the master, you should be more lenient about it (ie let him build the character he intends to play eventually). You could keep the student at the master's level minus 2 for that since it's not a long-term arrangement and the player will be taking on that handicap and catching up afterwards. The thing being a plot arrangement makes it less concerning from a balance standpoint.
If the player intends to just keep the student around as a sideshow mostly for flavor, I think 1/2 level is appropriate (obviously this is only a difference for levels above 4th; might make it Level - 3 or Level ÷ 2, whichever is lower). The student can be useful and can carry out certain other tasks appropriate for its own level, but wouldn't nearly be a substitute for a PC in a combat situation.
Otherwise you can just go by the Leadership feat's description of a cohort when he qualifies and actually takes the feat to account for it.

Don't adjust the party loot or experience for an extra character. The student's wealth should come out of its master's in every scenario here except for the basic starting equipment it enters with, and the apprentice's level is just dependent on its master's.

Leadership itself is generally considered to be one of the most (if not the most) overpowered feats in the game and that could easily extend to similar arrangements. Basically, if it looks like he wants to take on a cohort/apprentice for character optimization reasons, I would advise against allowing it under pretty much any circumstance unless the party is in desperate need of a Cleric or something (in which case I would still rather give them potions or a paid NPC). IMO extra characters should be reserved for character flavor or plot points and nothing else.