I sometimes wonder what's the least amount of money I could spend if I put a lot of money into capital that would save me money. For example, get a big solar array. Get a Tesla that I could charge at home. Get a hydroponic garden set up that would grow all my food. Save seeds. Dig a well. Solar water heating. Etc, etc. Obviously the upfront cost would be absurdly high compared to just going to the grocery store but it would be a fun project if I ever got enough money to do it.