Scaling down models is always easier than going up. You usually have problems with parts fitting on the page. Tat is the best advise, using the Search function, you will find some buildings suitable. This site: http://papermau.blogspot.com/ has some buildsngs, that because of their color and detail, would shrink down wonderfully!
There is a site that has tons of Disney paper models on it. http://disneyexperience.com/models/?page=1 this link will take you directly to the first model page. Look for the next page thingy at the bottom of the page because there are 7 pages of paper models in all. You will find Sleeping Beautie's castle, Cinderella's Castle, The Mark Twain Riverboat, the Big Thunder Mountain RR trains, The Main Street train station, all of the haunted house rides, and the list goes on and on. As far as re-scaling them goes if all else fails remember that a conventional doorway in N scale should be about 12-14 mm high, your mileage may vary.