In homes like this, sometimes this is just the tip of the iceburg.
You mention something about home inspectors going either way... This sound like speculation on your part and that you haven't hired one to look at this mess. I would not want to buy this house and inherit someone elses long-neglected problems (unless it is the absolute deal of the century and the actual cost of replacing floor/sills/ducts/etc. etc. is deducted). People get emotional about houses, I know, I have done the same thing. But hopefully you will hire a home inspector and you will listen to him and leave this mess for someone else to fix. It sounds like a potential nightmare.