When I first got into this business, not knowing anything about structural issues - except they could cost an arm and a leg to fix, I always was wary with my Buyers if a home had obvious structural issues. After-all, it is those unknowns that could make the difference if the home will be a "money pit". Over the many years, I have taken classes from structural engineers to learn more and more about these issues.
You will find many issues with properties that are nearing the hundred year mark, and in fact, one engineer told my buyer to RUN, don't walk from the transaction, as he thought the home only would stand (literally) for another 6 months, and should be scraped. I appreciate that information, and so did the Buyer! Sometimes it is obvious in the foundation, sometimes the floors are not level, or you see cracks all over the home. Not those coming from the corners of windows or doors, but vertical or horizontal cracks.
Don't get me wrong --- I AM NOT A STRUCTURAL ENGINEER! BUT, I have seen enough over the years that when I do see significant issues, knowing the next call should be to a licensed engineer if the Buyer wants more information!
What happens when you view a home that has had structural repairs? I always ask to see the documentation from the engineer who did the repairs, and present to my engineer, to get another set of eyes on the repair. If the repairs were done with a permit, and the City has approved it, the Buyer is probably good to go.
I know this, because MY personal home actually had vertical cracks, which I felt were structural when I bought it, but there was a 10 year structural warranty and still had 3-4 years left. The I-beam was off-center, causing lots of cracking throughout the home. The builder came back in (only after I had an independent structural engineer inspect) and repaired all the issues. After all was said and done - it cost the builder $30,000.
Not all issues will cost a lot, but should be repaired to prevent the issues from getting worse, and more costly!