Dad bought one of the very first JD 45 combines sold in the area (before I was born, he owned several 45's over the years they were made). Most at that time were still pull type combines and corn was ear picked by mounted or pull type pickers.

He said that first fall he shelled enough custom harvest corn for neighbors with it to pay for the machine. Not net profit probably, but grossed enough income to cover the cost he paid for the combine and heads. By the next year there were lots more self propelled combines around.

If I recall correctly the first 45's had Hercules engines instead of JD engines because that was back in the 2 cylinder JD days and they had not developed in line 4 or six cylinder engines of their own at that time.