I don't blame you, especially if there isn't an abundance of nectar sources. You might be surprised at how many hives an area can support though.
I have found that a lot of people talk about beekeeping, but when they find out the cost they start to think twice. Many think you just put bees in a box and come back for the honey, then they find out about varroa mites, feeding them, splitting them, and buying more woodenware, etc. So, while he may be interested, he may not be that dedicated. You could explain that you are still learning too and don't feel comfortable teaching someone else. Perhaps you should recommend a good beekeeping book for him to read? Or local bee club meetings or classes? That is when you find out how serious they are.
Something else to consider is if he becomes a 'bee haver' instead of a beekeeper, your neighbor may create a varroa mite bomb, or Foulbrood situation brewing that could affect your colonies.
Surveys show that a new beekeeper than loses their colonies in the first year or two is likely to get out of beekeeping. Sorry, I don't remember the exact percentage. So, taking him under your wing, should he fail, then he can blame you for his losses. Another reason to encourage him to learn on his own.
The up side is, he could get a bee suit and help you with the heavy lifting!