Complex sentence: In addition to selling his paintings, van Dongen also gained an income by selling satirical sketches to the newspaper'Revue Blanche' and organising very successful costume balls in Montparnasse to gain extra income.
Split into simpler sentences: In addition to paintings, van Dongen earned his money by selling satirical sketches to the newspaper'Revue Blanche'. He also organised very successful costume balls in Montparnasse to gain extra income.