Complex sentence: After a slow start to trading, Disney and Iwerks agreed that Disney should leave temporarily to earn money at the Kansas City Film Ad Company; the following month he was joined by Iwerks, who was not able to run their business alone.
Split into simpler sentences: After a slow start to trading, Disney left temporarily to earn money at the Kansas City Film Ad Company. He was soon joined by Iwerks, who was not able to run their business alone.