Cheryl,
If you don't have a smartphone that will take photos, you can get a 12 megapixel camera for $40-50 at Wal-Mart, Best Buy, and many other big stores.
There are a lot of gift return cameras on deep discount right now. I saw a really nice Canon, 12 megapixel, originally $119, marked down to $24.99 yesterday.
Ask the sales associate in the camera department if you can have a lesson before you buy. If you go in the morning, when its not busy, they will be glad to help.
Being able to take photos of stores, displays, gas pumps, and receipts is pretty vital to being a mystery shopper.