Apologies if this is answered elsewhere, I checked the forum but didn’t see the answer.
A few classes (Cleric and Elven Spellsword, for example) get unpaid followers who, at most, require minimal upkeep payments instead of full mercenary salaries. If/when these followers die in battle, do replacement unpaid followers show up, or are they just gone and must be replaced with paid mercenaries?
I didn’t see a rule covering this in the books. Is there an official ruling here? (For my own purposes, I think I’ll require an expenditure of gold equal to purchasing a slave of the same type/amount to replace such troops – not that the followers are slaves, but that they are economically equivalent and should require an equivalent expenditure).
I would not say they are equivalent. Fanatics that join you are far more loyal than slaves (plus, the PR doesn’t hurt).
As for your main question, I would probably be disinclined to allow quick or easy recovery of followers so fanatical. You can’t just throw money at people and expect to grow a zealot that will die for you.
I think the 9th level followers infusion is a bit of a one off freebie. You are an up-and-comer and people want to get in on the ground floor. After that, follower deaths shouldn’t make it EASIER to get new people to serve you for free (would you rather work with the widow-maker or the successful champion who obviously cares for his men?)
There might need to be some role-playing involved in new recruitment, at the very least. No free replacements to your free followers who you let die. This gives the followers more value, and doesn’t incentivise players to send mediocre followers on suicide missions (I’m not saying all players are munchkins, but you don’t want to encourage them).
Free followers actively seek you out when you build your stronghold and establish your new domain, but who is going to hear about your massive casualties and immediately think: “Oh boy, a job opening! I should high-tail it over there before someone else does and demand to work for free”? If anyone does, they are probably a bit… off.
That said, I think there should be some other way to get new followers, but it might come down to role-playing, deliberate effort, and work ranging from a process similar to acquiring henchmen to a quest in of itself.
Perhaps the domain could attempt a recruitment effort each month, making a “recruitment roll” (as with recruiting Henchman), including modifiers for the domain’s reputation. Also included as a modifier would be the amount of money spent on it (representing how extensive and far-reaching the promotions are. No matter how good your organization is, almost no-one will show up if they don’t know you’re hiring). The roll would determine how many 1st level NPC followers would show up to replace lost members, and whether they’ll require payment. No matter how good the roll, followers above the initial number rolled will demand compensation for their service.