I just noticed something that I never paid attention to before.
In one of my games I hired a hero with 3 Devils. When I exited and reentered the game my income per turn was lower (I noticed because it went from a number in the 400's to a number in the 300's). Checking the Devils upkeep cost I noticed it's 16 per turn and calculating the difference it works out to 48 gold. It appears the game is going to charge upkeep on my allies!
It seems a bit unfair that units you bought (or found in ruins) would then have an additional upkeep cost. That's definitely a difference from normal Warlords where allies you got with heroes and in ruins had an upkeep of 0. I realize this means tracking allies specially vs produced units but it's definitely something you should do as getting allies shouldn't be penalizing your income especially when they can appear in far off places (ruins/cities) and may cost hundreds of gold by the time they get someplace useful.
KGB