Complex sentence: To support his family he managed a chain of laundromats, until he got work as a cartoonist on an American weekly newspaper, "The London American", while Muriel started a business selling pinup posters.
Split into simpler sentences: To support his family he managed a chain of laundromats. He eventually got work as a cartoonist on an American weekly newspaper, "The London American", while Muriel started a business selling pinup posters.