How likely is mold indoors?

[silkcom]

I have a friend who used to grow "medicine" indoors and says that I should look out for the amount of mold that will come from growing indoors. I'm starting with just lettuce and herbs but hope to be able to do tomatos, peppers and cucumbers. How likely is it to get mold in such systems? I'm in the basement, but the walls do have drywall on one side of the small room. there's not a great way to vent the room, at least not to the outdoors.

Has anyone had any problems with this in the long run?