Since you are asking something of them that they don't necessarily have to do for you, I would pay for shipping back also. You do that with a SASE or you can just send along some stamps. But remember, you're never guaranteed to receive anything back; it's a risk you take, but if you get something back, even if its from another request, it's worth it.

In the US, the minimum for a large envelope is 88 cents, which is two stamps. I've found that if you're sending a SASE, letter and two 8x10 photo, at least 3 stamps will be needed. You can probably get away with two stamps on the return envelope, but if you want to be safe, but 3 on that also.

What country are you from?

If you are sending out of your country, you can buy International Reply Coupons (IRC) that you can send to the person. These are worth about one stamp at the country you are sending to. The person can take it to their post office and exchange it for their country's postage so they can send it back to you. If you are sending to another country, you can send everything (your letter, SASE, photos, etc.) with your own country's postage, but check on your Post Office's website for a postage calculator and rates to other countries.

I understand that I go to the post office and get stamps and put my letter into (forgot the word..). Anyways, how do I make the shipping? Would I have to pay for the shipping to them and back, or how do I do this ?