As someone unfortunately in the market for an old (60-80 years old) SFH due to the location I'm in, I'd have to strongly disagree. First, all houses settle and

As someone unfortunately in the market for an old (60-80 years old) SFH due to the location I'm in, I'd have to strongly disagree. First, all houses settle and a good rule of thumb is if it's not a horizontal crack, you're probably fine. The giant crack does sound worrying but that's not your typical modern home especially if you went with a good builder. Your house probably has loads of cracks that were sealed with epoxy and covered up (not a bad thing but it's not like your house is pristine). The "bones" of an old home isn't going to be better either. For instance, if you have a basement, you can't ever make it into a proper livable area due to the lack of moisture proofing. A rule of thumb is basements older than 1990s are probably not worth renovating into a living quarter due to this issue. And your house probably has had countless termite treatments which overall weakens the "bones" of your house. And don't get me started on asbestos, tube and knob wiring, or lead paint.