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If you were hoping to buy this trailer, please do not mourn over it. Someone else is will have buyer's remorse in the coming days.
It is a bit hard to really analyze from those few pics, and the FB ad is already down... But, I would say, that yes, it doesn't appear to have had any renovation done to it, and it is a 50 year old trailer; therefore, a project waiting to be tackled (money pit), and I can't see spending that kind of cash for it.
That being said, I guess I haven't recalibrated my vintage trailer cost scales for pandemic pricing, but rest assured, you will put tens of thousands of dollars into that trailer to make it nice. A few years ago, $15k would buy you a trailer that was ready to go camping. Something that needed to be extensively refurbished would be worth a few thousand.
What questions to ask? Simply, what has been done to fix it up? The more "original" a vintage trailer is, the bigger a project it is going to be to make it useable, especially trailers that have spent most of their lives in wet areas like the southeast or northwest.