Help with mailing a psp with USPS at a post office?

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.
First answer by Gregory2590. Last edit by Gregory2590. Contributor trust: 0 [recommend contributor recommended]. Question popularity: 1 [recommend question].