In order to understand whether to remodel an old house or simply build a new one, you need to understand the scope of work. And for this you with a piece of paper and pen will have to work around all the nooks and crannies of the building.
You should start with the Foundation. If the Foundation of an old house solid stone, the construction was dug a deep pit, the walls gave the crack, the Foundation will last a long time. So to remake it is not necessary, it is quite reliable.
Then go around the building around. If the house is hardwood, the logs are something which can rot, or crack. If such damage a lot, nothing can be done, will have to demolish the building and build in its place a new.
If the walls of the old house brick, solid, that can only be formed to patch up some cracks and potholes. For this you will need the cement mortar. Just apply the resulting gaps, so the building didn't collapse further. Then make the outer hull siding to cover unsightly old walls.
Then grasp the inspection of the roof. If it is leaking in several places, it is better to block it again. Now comes enough a variety of types of roof, which is easy to maintain and very reliable.
Don't forget about the gutters, fix the old, or attach new. Water drainage is very important, it prolongs the life of the structure.
Then you need to examine communication. Check gas appliances and the water system. If everything is working properly, the old parts were in time replaced by a new one, to alter nothing.
If all the system's old pipes rotted out of the tap is rusty water, and there is a smell of gas, then replace at least the pipes required. It will provide not just convenience, and security of all tenants of the old house.
Next, inspect the window openings. Most likely, Windows will have to be replaced with plastic. This will ensure quiet in the house and keep warm.
Only then proceed with the inspection of internal premises of the old house. You need to understand whether you need an overhaul with polishing of walls, flooring, caulking or simply pokleit new Wallpaper, and whitewash ceilings.
When you complete this tour of the building, make a rough estimate of the work. From it immediately becomes clear whether or not to undertake the alteration of old houses or will be cheaper and easier to build a new one.