Appropriately enough, he sells Knives for Excalibur Cutlery Co. While I’m not sure how much he’ll be using his sales skills as a part of X-Force (although he did get the job so…), knowledge of knives seems useful considering all the bladed weapons being sported by the team.
In that field he has risen beyond just a salesman to become an assistant to, nay a regional sales manager.
This could also be a fun reference to the Marvel comics mutant team called Excalibur that has boasted at times Colossus and Juggernaut among its members.
It seems that Peter’s primary experience and main job is in sales.