On December 6, 1993, at 1600 central standard time, a Beech A23- A, N6959Q, operated on a postpurchase positioning flight, impacted the ground on the left side of the runway and ran down an embankment during an attempted takeoff on Runway 30 at the Denison, Iowa airport. The airplane sustained substantial damage. The private pilot (right seat) reported minor injuries. The student pilot/airplane owner (left seat) received serious injuries. Visual meteorological conditions prevailed for the flight, no flight plan was filed. The flight operated under 14 CFR Part 91, and originated from Denison, Iowa approximately 1559, with an intended destination of Shenandoah, Iowa. The student pilot purchased the airplane the day of the accident. He had arranged with the private pilot to accompany him to Denison to fly the airplane back to Shenandoah after the purchase was finalized. He reported the private pilot stated he was experienced in the accident make and model airplane, and was prepared to fly the airplane to Shenandoah. The student pilot stated the private pilot performed the preflight inspection, then sat in the right seat. The student pilot reported "When I asked him about it, he stated that I had purchased the plane, so (the left seat) was my seat....I...asked...who was going to fly the plane, to which he answered 'I will.'....I began the takeoff with the understanding that he was on the controls with me." The student pilot reported he had difficulty during the takeoff roll and requested help from the private pilot. The student pilot indicated the airplane lifted off about 2/3 down the 5,000 foot long runway, and they began to climb out. He reported when he reached down to retract the flaps, the private pilot pulled back on the controls, stated "watch out for the trees" and banked the airplane to the left. The airplane impacted the ground on the left side of the runway and continued down an embankment. The private pilot reported the student pilot was handling the controls for the attempted takeoff. The private pilot stated about "...1,500 feet down the (runway) he turned to the left, then hard right off (the runway) and rotated at about the same time. Then the plane crashed." The student pilot reported 19.2 hours total flight time, with no experience in the accident make and model airplane. The private pilot reported 602.5 hours total flight time, with no indication of total flight time in the accident make and model airplane. Both pilots reported the weather was clear, visibility good, and calm winds. There was no evidence or claim of preimpact mechanical anomaly.