Be careful Amanda, once he learns a couple of tunes he will be looking on the classifieds for a guitarist and drummer and your neighbour may have a lot more to contend with. Then there is the GAS monster (Gear Acquisition Syndrome) where he will want to improve his gear as he improves, as we all know better gear makes you play better.
Seriously, I hope you both enjoy his new hobby and just remember there are lots of helpful people on here if he needs it.