Absolutely this. Just a note: Some surface rust is fine. But if it's rusty enough to cause holes and cracks, then it's a problem.

Older cars will be rusty to a certain degree, so being able to distinguish between surface rust and more severe rust is useful.

Surface rust can be scraped/brushed away and treated. If it's gotten to the point of compromisinh structural integrity, the only fix is cutting and welding in new steel, ir replacing entire parts, both of which can be very costly.