If both of his parents were non benders that kinda comes into question of how on earth he got his powers. Harmonic convergence isn't for another four months at the very least so it's not like he could have gotten it from that besides the fact that he got it when he was a kid. At least one of his parents or grand parents need to be benders or have noticed that they have the power to some extent. That's like saying Luke Skywalker was born the way he was and not because of Anakin is retardedly overpowered in the force.

That being said if he was poor then how did he get a teacher good enough to get to high intermediate? My guy was taught by two teachers both of whom where teaching him since he could walk and he is upper medium intermediate because of conflicting styles and his lack of refinement in specific areas. He can do things in mass but his force lacks for it for example if he threw a rock at someone he could hit them with the same force if he punched multiple rocks at them. The mercenaries could be a possibility but at the same time mercs wouldn't be near elite status unless they were really good at what they do. I'd say a more reasonable would be low to middle intermediate power bender. In my own opinion you're overestimating your character's power and I'm being generous in saying what I am because if my guy had that background he'd be middle adept.