I want an old man who likes me to help me pay the rent. He texted me and asked me what he could do.

Take your time. You can't just say rent or money. When chatting, you said you were upset, and he asked you what you were upset about. Just say what happened to your sister, borrow money from you, say that your money was borrowed by your sister for urgent needs, and then naturally say that your rent is about to expire ~ ~