I've had buyers back of out offers all the time.  Some are mannered enough to send me an email requesting that I decline their offer which I always do.  The replies here are right.  Ask seller a question comes first then you make the offer.  If this seller is trying to shove this purchase up your tail feathers, that's a red flag all in its own.  If you haven't paid, email the seller and ask the questions again.  He should have nothing to hide.  If he fails to answer, don't pay until you get the information you need.  That should solve the offer and the sale.