1 million.
I could basically be set for life with that kind of money. I would not immediately quit my job, but I would put that money in a safe investment and basically I don't have to worry about job security anymore. I'd expedite my plan to move off grid then probably quit my job within a few years after I've built something. With all my spare time I'd still look at ways of making money but basically I'd be free to do whatever I want with no urgent need for income.
On the other hand, it would still be a huge decision to make, because what if *I* end up with kidney issues in the future and now I only have the one. I guess it's a big game of odds. Most people live their lives fine without kidney issues so I'd just have to bank on that.