The seller should have survey. if not they have to get one

but it is between the buyer and seller to discuss who pays for it.

If there is issue with title the title company should alert you to withdraw the offer.

This is my point, DO NOT COUNT ON THE SELLER'S AGENT'S INFORMATION. I have seen all kinds of incorrect information listed by the seller agents, # of bedroom/bathrooms, total area, lots size, property taxes, you name it.

If the permit do not match, ask how this situation can be mended and for how much.