There is one other upside perhaps. The equipment you aquire to repair things can last a lifetime. The sooner you own it age wise the more money you save with it over the long term.

Another feeling I have after having done major rust repair. A car for one reason or another has to be really deserving of the effort. If the repairs required are really extensive a body swap is much easier on the head and wallet. A persons time has to be worth something and the hours required for extensive heavy proper rust repair mind the equipment and material costs can be unreal.

The metal in that rear dogleg is an advanced form of corrosion. Getting back to solid metal may be quite a distance. When you see something like that you want to really get a picture of the overall substructure condition underneath the car.