No, I haven't come across this curiosity in anything other than this one township in Nash County, NC in 1880. I remember looking at your Joel House's census record before, and that he was a free person, not a slave, which was why he was listed on the census with a trade. I don't know if you're aware of it, but there were quite a few free colored persons living in the US during slavery times, all freed for various reasons, or some may never have ever been slaves. The Evans families in particular was one of the earliest people of color to have lived in the South and many of them can be traced back to at least the early 1700's, if not earlier. So, it wasn't unusual to have free persons of color working along with whites, or working in their household in the 1800's. The key to researching them, is to check through records just like you would any white ancestors, by using deeds, wills, tax and census records, etc.