He wants me to put it on TrafficZ,
Is he planning on adding the domain to his account? If so, he will receive money for the traffic, either from clicks on the sponsored ads or through CPM.
Also, he may be from Trafficz and out recruiting more listing.
When he asked you to send the traffic to Trafficz, for monitoring, did he include a link with an affiliate number in it?
You can easily set up a parked domain with SEDO, or similar sites, and be able to monitor the traffic yourself and maybe pick up a little extra cash.
What should I look out for?
Also, if he does sell the domain for you, be sure to use an escrow service for the transaction.