4-5 years old, dad would block wood along fence lines and put the 1950 DC-4 in 1st gear with me steering, at end of field I would turn around and let him catch up. By 11 years old I was running 700 standard diesel hauling manure, 930 row crop pulling chopper boxes, and all the SC and DC"s moving feed wagons. Of course runnin the 990DB with loader or the 1845? Skid steer was the best treat. I view myself as on the younger side at 35 and wonder why no-one would consider putting a kid under 16 on a tractor anymore....very few of us would have any stories.