I haven’t tried the pro trial , and don’t want to incase I fall in love with it and can’t afford it, so to anyone with pro - do terrains cast real shadows on themselves? And are these shadows updated in realtime ( i.e. when different light sources come into play or the terrain is deformed ) … Just curious, long way from pro quite yet 
Yes, terrains self-shadow in real-time. Though there can be artifacts, moire patterns, flickering, and random disappearance of said shadows. Somewhat finicky.
Ok aways, thanks for the info
also keep in mind that “light sources” means you are in deferred rendering. Forward rendering only allows the first directional light in the scene to cast dynamic shadows at all
Considering that the terrain cannot overlap itself, there shouldn’t be much difference between pro and free with self shadowing terrain as Unity Free allows basic shadowing on objects, just no shadow casting. Of course, that means the trees and objects on the terrain don’t cast shadows in Free, but for plain terrain, there shouldn’t be much difference.