Four loads per day is getting to the point of a dedicated (electric) grinder or cracker and a part time employee who does that as a regular task.  It probably means a bin on each side of the grinder, augers or conveyors, and enough concrete to park a couple of trucks.  If you could get set up for $250,000, which is probably low, you would need about $250/hour to run it, or 25 cents/bushel if you could run it at 1000 bushels/hour.  The amount you are looking at is kind of in the awkward zone; not really big enough for a full time mill and not quite small enough for buying older, small equipment to run on an occasional schedule.
One other consideration is that ground corn is more prone to storage degradation than whole corn, so you probably won't want to work too far ahead.