I have been dealing with this quite a bit lately and as a result have become somewhat knowledgeable of how local jurisdictions handle permits.
#1 on the list is the ease in which it can, at least on a cursory level, be verified. Typically all it takes is a phone call and I have my answer. Maybe in some markets it is more difficult but so far my experience locally is it is just as easy as calling the assessors office. There are appraisers who have the notion that this is some kind of long process but have never stuck their foot in the water (or the last time they did was sometime in the 1990's) to see how difficult or easy it really is.
#2 on the list is how every local jurisdiction handles it. State law is permits are only required to be kept on file for 10 years. So far, while most jurisdictions will quote state law, they do keep records for longer than that. Currently the furthest back that I have found in my local market area is 1986.
#3 is specific to my state as we are non-disclosure. Things like data cards for a property are not readily available. I can make requests to the county attorney but this is typically a 5 to 20 business day process from the time they receive the request in writing. In addition, there are additional fees associated with getting these documents. So attempting to verify GLA, age, etc is not something which can be done in the normal course of business. In states where full disclosure is allowed there may be no reasonable excuse.
#4 is also specific to my market. While local jurisdictions can tell me if permits have been issued, what they were issued for is very generic. At times it will be a comment like "a 1 room addition". Sometimes I will be given "an addition of approximately 500 sqaure feet". While I can make some educated guesses as to whether the permit is for what I am calling for, the non-disclosure status of law prohibits me from knowing for certain.
My biggest issue with the whole permit thing is once I have been asked to verify a permit, am I not responsible for verifying all permits? What if the elctrical has been updated or the hot water heater/furnace replaced? What if the windows were replaced or the entirety of the kitchen redone? I can tell you in most local jurisdictions in my market, this requires a permit. I just wonder if I am opening a can of liability beans.