I enjoyed your post. However, I have to disagree with the following sentence:
"There just aren't any homeless people who are really smart."
First, unless you have experience with a statistically significant group of people who are homeless in many different areas of the world, it's unlikely that you have enough evidence to prove that there aren't ANY homeless people who are smart. This is a hasty generalization and a fallacy in logic.
Secondly and more importantly, it's an assumption that is damaging to those who happen to be homeless and are trying to improve their lives and change their situation. It's harmful to make stereotypes like these -- and even more harmful to spread the stereotype in writing.
I work in a program where we provide free university-level education for people who are homeless, and I can say as an educator that I have encountered many very intelligent people who happen to be homeless. Many go on to law school or graduate school to become educators themselves. They are very intelligent and have proven it, both in and out of the classroom.
There are many different reasons that people become homeless. Having a lack of intelligence, I think, is not one of the most common.