His debts became an invisible prison-house, preventing him from chasing his dreams.

prison-house 是由 prison（监狱）和 house（房屋）组成的复合名词，字面意思是"监狱房屋"，比喻为"牢笼"或"禁锢"的状态。这里用 prison-house 形象地描述债务对人的束缚作用，就像被关在监狱里一样无法自由行动。