What does not show in the listing photos
Post bases that have sat in soil or manure. Truss connections that were never plated for the span. Lean that has been there so long it looks like character. A kit barn that was 'designed' for a different snow load. A conversion to a shop or event space that added occupancy the frame never had.
A home inspector may note some of this. A structural engineer is looking at capacity — what the building can still do, and what it should not be asked to do.
Before you close
If the barn is part of the reason you are buying the property, it is part of the due diligence. Bob evaluates existing post-frame and timber barns across Southern Indiana and will say plainly whether the building is serviceable, what should be repaired, and whether a new use needs design rather than hope.