All I can add to T-Mar's excellent post (as usual) is that the factory did use white primer on several period frames I have seen. When deciding if you will take a deal offered don't forget to the painting costs $50 for decals.
A low cost refinish by a frame painter will mean you are going to need a serious discount on the price paid to be better than returning and keep looking.
As to your situation with the seller, if it was Ebay, I would try to argue that the frame being stripped of paint should have been disclosed and therefore the frame is "not as described" and seller must pay return shipping.