not have a bean - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Be destitute or penniless, as in He doesn't have a bean, but she's set on marrying him. Bean has been a slang term for a guinea or a sovereign coin since the early 1800s. The precise expression was first recorded in 1928.