I am wondering if it is possible/reasonable to replace only one side of a house's wooden siding at a time. The problem is the indecision as to which route is the best for the longevity of the house and our pocket book. We could afford to replace one side at this time but is this even feasible?

Built in 1902 and purchased in 1973, my parents refurbished the house during the 70s keeping everything as original as they could; unfortunately time has taken its toll. The houseís tongue and groove siding is mainly the original with some of it being replaced in the 1920s as far as we can tell. The weather side of the house is rotting out; however, it has two layers of siding between which water has begun to enter the house. There is no sheeting or moisture barrier underneath the siding and the blown in insulation has begun to sink; obviously this needs to be remedied. The windows are also the old sash weight with original glass covered over with storm windows; these will need replaced also. It is terribly overwhelming and I donít know where to start or what to go with.
Sincerely, Allison