in Spanish -at least in Spain- we have a wide range of expresions to say "I am very poor" (no wonder why...), like the following:
Estar sin blanca.
No tener donde caerse muerto.
No tener un Real.
If you don't like any of these idioms wait for more posts. As I've told you there are a lot of expressions in European Spanish to convey this idea, and probably in South America they have some more (in fact, idioms related to 'pesos' must be South American, since the peso is a South American currency).