Please grab Edi's spreadsheet from the
Units, Weapons, Armor link in his sig.
Recruits and Summons: the "Cost Gold" column determines maintenance, at (Cost Gold)/15
Mercenaries: the maintenance is zero
Pretender: I have no idea if you have to pay maintenance on your pretender
I think it would be nice if "Cost" and "Maintenance" could be added to the "Hit Points" window so that it looks like this:
Hit Points: 10
Size: 2
Cost: 24
Maintenance: 24 / 15
...