I don't think it works that way.
A "minion" isn't a thing that exists, independent of the PCs, anywhere in the world. There are no free-roaming minions wandering around cities - "minion" is just a description of how the NPC or creature interacts with the PCs in combat. That's all. Of course he doesn't know he's a minion. His bodyguards also don't know they're "brutes."
As a DM, you could certainly declare that this tax collector acts as a minion in combat, but again - if you do so, you're doing so for unusual narrative reasons. "This tax collector is completely feeble in combat, and doesn't present any real threat. A good, solid blow to the head should knock him out."
He's not a minion because it's the way the world works, or because of any characteristics inherent to him. He's a minion only because the DM has determined that's how he'll interact in combat with the PCs, should said combat occur.
-O
My earlier example of the housecat was just that, one example of how pretty much anything in the game world that can do 1 point of damage could spring up in any session and really have your minions on the spot. I'd just like to have it sorted beforehand.
This is actually my main question now. "Do minions only have 1 HP when dealing directly with PC's, or the entire game world? It's an important question. If the answer is 'yes' then again, is this just an assumption or is this RAW? I haven't seen it. If the answer is 'no' then consider other situations like the following.
A good point was brought up about terrain and damage.
Let's say you have another perfectly reasonable situation.
The PC's are say, in the middle of a forest, on a hill (for no particular reason just to help with description).
Running to the PC's, are some townsfolk being chased by demonic minions, screaming 'save us' as they might do.
Between the PC's and the townsfolk are... wait for it... 'THORNY BRAMBLES'!!! Oh noes!
The townsfolk, knowing they'll get scratched and take some damage through the 15 feet of brambles (1 hit point damage per 5 feet while running, no attack roll) do so anyway, because they know they'd rather face some thorns off a bramble bush than demonic minions from the nine hells.
The townsfolk push through, albeit a bit scratched up. The PC's ready themselves for the demonic minions... who either cower at the sight of that undergrowth of minion death, or wade their way through, being destroyed by those damn bushes yet again!
In fact, if you have a battlefield where minions are part of your enemies arsenal, all you have to do is surround your troops with terrain that provides one point of damage with no attack roll and you've pretty much got in incredible advantage.
Now keep in mind, if you take the approach that 'minions are only minions when interacting with the PC's' then ok, you could almost follow that line of reasoning and get away with it but you'd have to make exceptions to this rule, and exactly how are you supposed to deal with it if you take that line? For example, in the brambles above, do you kill them off? Do you say the brambles just don't do any damage at all? If so, why? Isn't it now unfair that the PC's themselves would take damage walking through but the minions don't?
Ok go RAW and you have a very silly situation. Demonic minions can't chase your average barkeep through damaging terrain of any sort that does automatic damage. Adjust the rules on the fly and you have another problem with consistency. A 20th level minion running through brambles doesn't take damage but PC's do. Maybe not such a big deal but still slightly unfair and could have other consequences. I've got no real issues with explaining things away and roleplaying combat situations out like this for them to make sense, but RAW, the fact is, 1 HP minions unfortunately don't make sense in some situations. If I'm wrong, so be it, but if you're talking about it as RAW then please show me where it's printed. I'm sure most of us here can explain things away at the gametable, but it's the RAW that has me confused.