I agree with Mr. Skeptic.
If you are searching for some foundation for accurate first-encounter judgement, I don't suppose you will find anything. You may however be able to find many good probabilities on the subject. For instance, A unshaved, long unwashed hair, and dirty faced man has a high chance of being homeless. However, this is not 100% conclusive.
In addition, many people where a "mask" and disguise their true selves to some degree and this information is near impossible to extract in a first-encounter scenario. So you are stuck with simple probabilities but nothing definite.
Unless thats what you are searching for...
