Impecuniousness is the state of having very little money, especially over a long period. It is the noun from impecunious, and it is rare and formal. When writers use it, they often do so with a small smile — it is a grand word for a thin wallet. You would not normally use it about serious poverty in real life; it can sound too light. Everyday English would say poverty, or just being poor.

窮困、囊中羞澀（偏書面；日常說「窮」或「沒錢」即可）