The $38 garage sale house in Muncie that turned into a 3-day mess

I drove out to Muncie last Tuesday to look at a 1911 four-square listed at $38,000, and the whole trip fell apart in stages. The seller never mentioned the back half of the roof was soft, so when I walked the upstairs hall my foot went through the ceiling of the kitchen below. I still spent the next two days pricing out a new roof and a joist repair, and it came to $19,400 just in materials, which kills the whole point of a cheap house. So now I'm sitting on a quote and a decision, and I keep going back and forth. Has anyone here bought a place where the roof ate the entire budget, and did you walk or find a way to make it work?