controlling mold in greenhouses?

I do not yet have a greenhouse, just planning for the future once i'm on land I can put one up. (currently in the city, trying to move to rural)

One big concern I have especially about a year round 'permanent' indoor food forest is... aren't I going to end up with a serious and unkillable mold problem? :P Is there some way to avoid or deal with this? Different things grow in different humidities, I could have one place dryer than another if separated and set up right, but thats not a fix for things that need a humid environment.