I agree with Drew. Your fellow will be perfectly fine at doing low levels.
Just keep an eye on any signs that tell you that he is at his limit.
Remember, Jumping isn't the be all and end all of riding. In order to do either Jumpers or Eventing, you must have ALOT of Dressage under your belts to beable to compete at the low levels and be good at it.
Jumping is dressage with Speed Bumps - and in the Eventing World, Dressage is the most competative and difficult stage in this sport, and if you do not do well in your Dressage Phase, you will struggle to place top 5. When you compete, you'll be riding amongst many who spend hours doing Dressage - so be ontop of your game.
GP Jumpers spend up to 4/5 days a week doing Dressage and their horses can do minimally level 3 movements - so keep that in mind as well when you start training.