I dont think this sort of discussion is to be held here. Though, lets go:
The only factions which get passive income, to my knowledge, are the Gendarme and the Vallaki Guard. If you give these two passive incomes, it should be extended to the:
Theatre
MLers
Ezrites
Gundie Rebels
Erudites
This would be fair and equitable, but I can find no good reason to give any of these factions passive incomes as they are free to travel and adventure as they like, unlike the Guard and the Gendarme which really frown upon that sort of activity.
Vallaki Garda and Gendarme while limited in their actions do get to pocket all the gold from fines and whoever they might arrest if corrupt enough. As for the factions mentioned, IMO:
Theatre - IDK much about it to have an opinion.
MLers - Yes, this is also "work", albeit religious.
Ezrites - Yes, also "work".
Gundie Rebels - No, as freedom fighters I don't think they would get stable regulated payment.
Erudites - IDK, maybe? They are an institution, AFAIK.
Being a Garda or Gendarme is an actual job--hence, IC justification for receiving income (I wouldn't even call it passive).
Otherwise, presumably room and board would be plenty of "pay" for the undefined duties faction members might perform within other factions.
Being in a faction is a disparity already with other PCs that should not be increased. If the passive income is trivial, why bother? And if it is not, then it would be a source of grievance.
Money-making opportunities abound in game already with the most minimum of efforts such that players frequently call for gold sinks and decry the worthlessness of so much of the loot table.
Most official factions are also actual jobs. Lawgivers perform religious work. People in the Red Academy do lectures. While most factions are entitled to do dungeoning and thus get rich easily and quickly, some players opt out of it and choose to focus on the RP. Not everyone is out there to go out and kill stuff for the sake of enriching or any other motive. Fresh members of the Red Academy who devote themselves to RPing mostly and are low level would benefit the most. It is also detrimental to low level RAs to remain banished from Vallaki, which per design is the railroaded start for all characters, it is where low tier content is easily placed.
Giving a bit of commodity and love to people who dedicate themselves in less active domains, and on the same time keep supported factions alive regardless of the domain, shouldn't be a source of grievance, rather the opposite.