The move comes on the heels of another rules change instituted by the GSEs late last year. A Fannie spokesman has said his company is concerned that some resort condo structures do not live up to the requirements that they be residential in nature. In the past, Fannie has been more active in resort lending than its secondary market rival. Indeed, the call for loans on vacation properties is increasing at twice the pace of that for primary residences, according to the latest tabulation from Redfin. Perhaps that’s why 15% of all newly built houses these days are vacation properties, as the National Association of Home Builders reports.