We have the option of selling a home we own (but don't currently live in). It was built by my grandfather in law in the 1950 so over 70 years old. We could sell it for market rate (bout $1.5M) or renovate it (making it much larger, better layout, etc) for about $600K.

I kind of rationalized that the house is still solid after 70 years, I know pretty much every inch of the superstructure now, so why not just renovate?