I was noticing something during one of my campaigns that I wondered if anyone else noticed. In Brandybarrel's FAUST guide he talks about units that are 'Free City Garrison.' In the guide, pretty much any unit that is a militia unit qualifies as a free city garrison. In other words this unit does not get charged to your faction when it is garrisoned.

But I need to qualify that - the unit must be garrisoned in a city to qualify for the 'no charge'.

From what I've seen in the game there are a few qualifications on getting the freebie garrison unit. First, you only get the 'no charge' on militia garrison units in a city. You DO get charged for them in castles.
Secondly, you only get the freebie for the first three militia units posted in a city. The fourth unit of militia spearmen, or militia whatever, is charged to your citiy's expenses and you're paying for him.

I going to assume Brandybarrel has already noticed this qualification, and I'm just a Johnny-come-lately. But you definitely do not get an unlimited number of free garrison units.

Anyone have anything to add? Or any remarks to my observation?