You Analytics code is what you use to help track your site traffic through Google Analytics. [More about Analytics here] As far as giving your code out, did you ask them why they needed it? That would be my first response. While having access to the code alone will not allow them to get to any of your private payment data I still wouldn't recommend giving it out unless they had a legitimate reason to have it.
Not sure if this is quite the same as giving your analytical code out, but I know that when I'm interested in buying a website, I usually request that the seller add me to their analytics account if they have one.
yes they want me to add them to my analytical account, I don't mind showing them one campaign(the one their thinking about buying), but can I hide my other campaigns. Edit: Ok, I'm kinda embarassed. I just checked my analytics and I don't have any sites set up, can they still get the analytics?
Nope, you need the analytics code installed on each page of your website (or just the ones you want to track). This means that no data will have been recorded up until when you install the code. Also you don't need to give the code to anyone other than your webmaster, you can grant them access via the admin settings. If you have any questions on doing that, then fire away.