If you love the house and plan on buying this, get a Home inspector, he will suggest getting a Structural Engineer to evaluate everything and say what needs to be done, next you get a few estimates from licensed contractors to repair everything and if the homeowner not willing to fix everything, negotiate the price and ask for a good amount of credit for the repairs and do the repairs yourselves.

If you don't want to deal with all that and not in the mood for a little adventure :-) walk away and look for something better.

Good luck

Last year we purchased a home much scarier than that. We justified a much lower price based on our willingness to correct many of the flaws (wiring, plumbing, unlined fireplaces). We also had a detailed home inspection as a contingency of purchase. When the inspection found a septic issue, we had the sellers correct at their expense. We also went through the list and told the sellers which flaws we were willing to correct and which we expected them to correct to complete the sale. This seemed like a reasonable compromise to them . Most of the repairs came in under budget! We wake up every morning happy and home! When you submit your offer, include a letter detailing the reasons for your lower offer—“ replace knob and tube $——-, replace galvanized plumbing $——, reline fireplace $———, etc.”