Seriously, though, unless you're planning to open a bed and breakfast, why buy such a big house?
More to clean, decorate, heat and cool, insure, etc. I've had one of these monsters, and unless cleaning and decorating are your favorite hobbies (hey, those people do exist!) I think you should pass on it. You can only use one room at a time, after all. Oh, as an added bonus, all repairmen and service people will charge you higher rates as soon as they see how big your house is . . . I guarantee this.
imho you should NOT buy such a big house if you require a 30 year mortgage to do so. Buy something you can afford with a 15 year mortgage instead.