there are property release forms that exist ... but you probably don't need
to have anyone sign them if you don't plan on selling the images and making a commercial effort from the images. if the folks to say it is okay to photograph their structures, maybe bring them a print as a thank you
people love that sort of thing -
whenever i go and take portraits of strangers at work, i don't have them sign anything, i just bring them a print. most people don't really have anything bigger than 5x7 or 8x10, so when they get a nice portrait on 11x14, they are pretty happy ..