The college students didn't think they'd have enough money to pay their rent. They sold some stuff and borrowed from their parents and they finally scraped together what they needed just in time.
Meaning: The expression "to scrape together" means to gather together or make something with difficulty. The expression is used when trying to collect enough of something from limited resources. Most commonly, as in the case above, it's used with money.
Christina: There's nothing to eat. Want to order a pizza?
Lisa: I'd rather save money. What's in the cupboard? Maybe we can scrape something together.
Christina: Not much. There's some pasta.
Lisa: Great! Is there any olive oil?
Christina: Yeah, I think so.
Lisa: And this tomato is good. We have dinner!
Meaning: In the second example, Lisa says that they can "scrape something together", meaning dinner. This means that despite Christina saying there is nothing to eat, Lisa thinks they can gather together enough food to make them dinner. Also notice that the expression can be separated with a noun.