OK, so we did this ourselves and it took one and a half years and a whole lot of blood sweat and tears. Firstly, I'd say you should get an engineers report to see if the building is structurally sound, as banks will not give you a mortgage on any property that is not. Also, depends on how old the property is, I know many places won't insure anything over 100 years old, mine is almost 300 years old! If it is sound, then you start the fun part, ripping it out and starting again. Depending on how good or bad it is, we ended up with floors down to the dirt and put in DPC and poured new floors, new stud partitioning and plastering, entirely new plumbing and electrics, timber ceilings..... aargh it was so much effort, but I now have a house that is totally unique and that has a real "wow" factor, it is so worth it, but if you are not going to do the lions share of the work yourself, it can be expensive, I am lucky H2B is into restoration.