While snooping around yesterday, I found this little item. It seems the Castle is on the list of
"National Register of Historic Places". I wonder if that would have any bearing on the saleability of the Castle..ie Covenants, etc.
(Can't do dis, must do dat...) 
NB
Number 24 on the list in Belknap County, NH:
http://en.wikipedia.org/wiki/Nationa..._New_Hampshire