You are only passing one variable into your function:
PropType. But on the first line of your function, you refer to a variable named
PropClass. Your function has no idea what this variable is, because you haven't defined it inside the function, and you haven't passed it into the function as an input. It sounds like you want to do that, so your function's first line should read:
def reclass(PropType, PropClass)
And your function call should read:
Side note: your variable names do not need to match your field names, that may be part of your confusion.