Not sure about TrafficZ, I have had no dealings with them.

Firsr of all - ***Under no circumstances should you change any of the contact information for the domain to this person!***

I just looked at the TrafficZ website and an account there is free if you meet their requirements. Why would you pay 10% commisssion if he is just going to list it there for you or did he explain all the things that he will do to sell your name?

Just from the info you gave here it sounds as if you have a decent name that he wants to add to his account to get the additional parking revenue?

Could I lose the domain? - As long as you do not change any of the contact information, do not give anyone the EPP Auth code, and keep the registrar lock on you can be reaonably sure that you will not loose the domain.

There are still ways you can loose it, but if you do the above you wont give it away to this guy who wants to "help you sell your domain".

Maybe I am wrong about this but usually you dont get approached by someone unless they stand to gain from it.

Just my 2 cents,
Mark