Answer:
Okay, I just sold something on eBay and the guy didn't pay me yet. In the case he doesn't pay me tonight, I won't be able to ship it tomorrow. And tomorrow the shipping label I printed from eBay is the only day that it's good. So in the case that happens, I'm going to try to go to the post office and ask for a box(will I even have to pay for this?) with his address and everything.
Now my question is, how much stamps would I need if I was sending a small package from NJ to California?
In case you're wondering, the thing I'm sending is a PSP.