If Adam doesn't get enough satisfaction out of housing Bob, he needs to do something else with his basement.
Adam ought to enjoy that Bob has heat and can afford college. If not, he needs to do something else with his money.
So Adam should either give these things away for free or not sell them at all. With only these choices, the world is going to be significantly more miserable. In an attempt to keep Bob from being 'exploited,' Bob is going to end up cold and homeless.