You really need to get a builder to have a look at it for you. This could be anything from 20k to 100k+, depending on lots of factors.
The last one I looked at was for sale at around 70k but wasn't worth doing. Any wood in the house would have to be stripped out, new roof, electrics, central heating, replaster, new kitchen, floors and decorating, and cavity insulation. Line chimney, install stove. There was potentially an issue with septic tank, a private well to be sorted out, about 30 very mature trees needed to be cut, and a proper boundary established. All to end up with a relatively small house worth maybe 150k.