...I know you're new here and all that, but I gotta be honest with you. No-one is going to hire you. Nearly every hardcore nerfer is going to have a highly-modded blaster that will manage to overtake you unless you have something to match them, and even then, said nerfers would rather handle their opponents themselves. Besides, Nerf isn't simply about winning, it's about having fun. And no-one is going to be so obsessed with winning that they'd hire a mercenary, as many things from actual warfare don't transfer over to Nerf.
Tanks exist in real warfare, but we don't use them in Nerf. Why? Because the concept of a tank (an armoured, well-armed box with an engine and treads/wheels) simply doesn't apply to how our hobby works. And when 'tanks' manifest themselves (almost never), they mostly amount to riding into the battlefield in a pickup truck with a Vulcan on it (and that only happened once, in Australia).
Likewise, the idea of a mercenary doesn't apply to Nerf either, because surprise, Nerf guns don't kill people, so it's no big deal if they get tagged out, and paying someone money to come and fight for them is rendered redundant when they simply can play a team match and have half of an entire Nerf club, essentially, for absolutely free.