Which one is more common, please:
"How long are you married?"
"How long have you been married?"
The first would be wrong in Canadian English.
I don't find it natural at all.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
I'm not very good at geography (), but might this have been in a part of the USA with a strong francophone backgrround (e.g. Louisiana?) I've had French students who had trouble with this point.