I don't own a house here in the Bay, I dump everything in very diversified index funds and some rentals out of state, since I'm not interested in staying in this place long term and play the million dollar mortgage roulette.
The day I call it quit, me and my partner (she does well too) can move to Austin TX, or anywhere else really (we're both immigrants with citizenships in really really cheap countries), with our fat liquid assets, and not having to worry about necessarily finding work in my 40s. At least that's my very optimistic plan, it might completely not turn out like this, or I might die tomorrow.
So it's really not that much, most people who get private or state pensions get a better deal than that from a cash-flow perspective.
Edit: sorry for the ninja edit. I read your comment too quickly.
1) If you keep it under your mattress it will be much less than what I described, because every year your nest egg will shrink due to inflation, so you'll just be able to take $25k non-inflation adjusted, which is a big difference from my $25k inflation adjusted (in 60 years, $25k will be $150k at a 3% inflation). My assumption is 0% real growth, not 0% nominal growth, which is what you'd get by keeping it under the mattress.
2) The 4% rule is based on a shorter retirement interval (30 years) than what I'm looking for (60 years). Try to go on firecalc.com and look for the statistical odds of 1M giving you 50k/y for 60 years: the failure rate is higher than the success rate, and that's based on historical data.
3) Yes, my assumptions are very conservative, but I don't believe index funds will return 7% nominal over the next few decades, the world is going to face too many problems in my opinion. That being said, pretty much all I have is invested in index funds despite my opinions (mainly because I wouldn't know where else to invest it, since both cash and bonds are sure losers to inflation), so in the best case I'll be pleasantly surprised.
Again, quite possibly I'll die much younger without even enjoying any of that freedom :-)