I think we have very different ideas of what "FU money" means. FU money is literally enough to be able to do what you want. It's being able to stop asking "Can I afford this?" because you definitely can. It's being able to stop making a choice between two sports cars because you can afford both. It's being able to buy the exact house you want because you can approach the current owner and make an offer they'd be stupid to turn down. FU money is literally the ability to say FU and do something anyway when someone says you can't.
Having enough money to retire a bit earlier if you live a relatively simple life and save a lot is not FU money.
$750k off the back of a $180k investment. Is this not FU money yet?
$750k is barely the down payment on a nice Bay Area family house. Of course it isn't FU money. You're not saying "FU" to anyone if you're also saying "I can't afford the house I want so I'll choose a more reasonable one."
FU money is being able to say fuck you to anyone (including your boss) without consequences derailing your life.
At the very beginning of my career I worked in the lab for 36 hours straight trying to finish a project on a tight deadline. I didn't have any "FU" money at that point obviously. If someone asked me to do that today, there would be no way! I wouldn't quit over it necessarily, but I would still be OK financially if I was fired for saying "your deadline is ridiculous!"
So how much does it cost to travel to Alpha Centauri and back?
There are always things you can't afford, no matter how rich you are. So that's a bad definition.
I always thought FU money was enough money that you can say FU and not do something when someone says you have to. That is, enough money to retire (get fired) on a whim. Of course, even by that definition, 750k isn't FU money unless you're single in a LCOL area (or fairly close to a predictable death, I guess).
My personal criterion for FU money is 3mm. This is fairly achievable, market willing, if you have make six figures.
in the U.S working a regular but relatively high paying job like developer should give you FU money right about the time that you start to experience health problems that will then eat into that FU money leaving you nothing.
There's a reason the song is Birth, School, Work, Death without any FU inside the comma separated list.
You might want to update your models. If interest rates will remain at 0 (or get negative like in Europe), you'd be lucky with 0-1% return.
1. Reduce outgoings. It's easier to have FU money if the amount you need to be able to say "FU" is smaller, because you've perfected the art of living on a little less than most. Most people's outgoings grow to meet their incomes: resist that. You don't need to recycle everything you touch and grow your own food to make good headway here.
2. Take your age, halve it. That number is the percentage of your gross income you should be putting away each month into retirement and savings if you haven't started already. Yes, it's hard at the beginning, so have it happen automatically through employer deductions (common in the UK for pensions, not sure about elsewhere), or on payday move a %age automatically into a savings or investment account so you get used to living without it. I still struggle to do this but am getting better.
3. Learn about compound returns a little more. $500 a month at 8% (typical market returns recently), and over 10 years gives you back $92k - a $32k profit on the $60k you put in. Whether that's FU money is dependent on whether your outgoings are $50k/year or $150k/year. Keep going for another 10 years, and you're not far off $300k which isn't bad for the $120k it cost you. Think you can keep going into your fifties and do another decade? $750k off the back of a $180k investment. Is this not FU money yet? You're the problem, not the regular job.
Your chances of having FU money working a regular job are far, far higher than having it any other way. It's just too many people are trying to retire in their 20s and not getting it: that's not a very likely outcome, no matter how hard you work or how smart you are.