In the past lenders have not cared if you permitted an addition to your home or not.  However some lenders are now asking for permits as a condition of loan approval.  This has delayed many closings as it has caught all of us off-guard.  If you are buying a home that has had additions added to it over the years, please make sure to put in the contract that the seller will provide a valid permit for each addition.  The seller might have to have it "back permitted", that is have a permit issued for work done 5-20 years ago, and that is not a quick process in some cities, and it is not a free process either!