You don't want to sell to "investors". Investors are looking to buy for cheap/below market and then either flip or else rent the place.
Fix the foundation and the roof and list the house for sale just like any other house. Sell it to a normal person who will pay full pop.
This is pretty basic stuff. Your husband is, no offense, being an idiot. Sure, it could cost more to fix, stuff comes up with any kind of renovation. That's life. It's not going to cost the $80k less you've been offered.
-W
Although this can depend on your area. As I mentioned in another thread, the house I use to own, like most recent sales in my old hood of smaller older homes, were sold for the high land value, razed and mcmansionized. So no amount of improvements would have increased the value. The little 1000 sf 1950s house is being turned into 2 houses on one small lot with 9 bedroom and 9 baths. YIKES! Investors are buying these up like crazy. $600k for a hunk of dirt.
The OP said that banks won't finance, once banks are out, it's only the investors. Not many investors are going to pay $600k in cash. In order to do that, the investors need to find hard money lenders, those have higher interest rate, first, and second it's a large home with already a long list of repairs from the owner (investors might make it even longer in order to sell for high dollars themselves) and hard money lenders might think that it's too risky since so much work is needed and ask for even higher interest.
The improvements will get the banks on board, and obviously more buyers. Most investors won't touch it, if they don't make at least $20K, and that's including carrying costs (the longer the list, the more time it would take, the higher the carrying costs). $80k minus $23k, minus paint/carpet/countertops, closing costs, carrying costs, and you get to about $20k (doesn't seem too unreasonable to me). Some unexpected problems might even dig into $20k profit. I was very surprised to learn that replacing soffits, fascia, and gutters costed as much as roof replacement (that's an example of an unexpected problem). And that's not accounting for the problems caused by the creatures that lived in the attic that I wasn't aware of at the time of the purchase. Buying a house as is (no inspection, like in this case) is very risky.
On the other hand, it's $23k vs. $80k, I think $23k wins.