The pilot arrived for the morning cargo flight with the twin-engine airplane parked directly into the sun and condensation on the windscreen. Using his hand, the pilot attempted to clear the condensation from the windscreen only to have it reappear. The pilot elected to start taxiing with the left crew door open to aid his visibility; however, while executing a left turn onto the cargo ramp the airplane's left wing and left propeller impacted an unattended airplane. Once both engines were secured, the pilot was able to exit the airplane unassisted. An examination following the accident revealed that the parked airplane sustained structural damage to the forward nose area, and the taxiing airplane sustained structural damage to the left wing.