Pics are definitely daunting. Not bought a house before or got anything to compare to, so really hard to benchmark or come to a view, or put a number on repairing it
Is there a particular reason you're going for places that need such work? Are you planning to do it yourself or get people in. How are you planning on funding it, you won't be able to get the mortgage to cover any of the additional costs needed.
Mmm. Some chunky stuff there. The potential for the flooring and supports to be rotting / infested would worry me the most.