Hey Everybody!

My wife and I had our offer accepted on our first investment property. It is a duplex in a great part of town that is nearly turnkey. Our offer was $15,000 over asking. The inspections came back earlier today and listed many minor issues but did reveal a few concerning items. The home has a crawl space which revealed a significant amount of water damage to the stringer joists and parts of the floor framing. Additionally, they recommend installing new vapor barrier. They seem to believe that all of this moisture damage is related to a lack of proper guttering on the sides of the house. There also is visible fungus on the beams and evidence of past termite infestation and subsequent treatment but no evidence of active infestation. 

Looking for advice on how to proceed? Obviously these findings are not things we could have easily seen on walkthrough and likely will be quite expensive. I've been given rough estimates of somewhere in the 15-20k range although we just got this information back today. Would it be better to ask for reduction in offer or for the seller to pay for the repairs directly? I think the required repairs may be more than a credit would allow for but I could be wrong? 

The numbers still work with repairs up to $25,000 but given the great condition of the home otherwise we were disappointed with the findings in the crawl space and don't want to have to walk away from the deal. Any advice would be appreciated!