$4k/mo post-tax ~ $6k/mo pre-tax == $72k/yr. There are a lot of programming jobs in the US that don't pay that.

And those jobs are going to want you to work, so a better comparison is to a pile of money that throws off $4k/mo post-tax. If that pile of money is invested in blue chip dividend-paying stocks with an expected return of 5%, you'll need around $1m to generate $4k/mo in passive income. (Obviously tweak your expected return and the corresponding principal required to fit your assumptions of market performance.)

$1m may not be FU money to you, but others will disagree.

I think you are misunderstanding the point. It's not that he was saying 4k a month is FU money (although it could be) its that since he ostensibly already has FU money he can turn down 4k a month so he doesn't have to compromise his principals.

That said if you have zero debt, low expenses and a ton of money in an account that yields 4k a month in interest, 4k a month could be considered FU money.

In this case, how much of the 4k should be re-invested to counter the inflation?

That's a function of both inflation rate and your expected ROI. Using 3% inflation and 6% ROI you need to reinvest ~51.6% of your income to break even. (1-(ROI-((1/(1-inflation rate))-1)))/ ROI = 1-(.06-((1/(1-.03))-1))/.06 = ~51.6% Edit: Ok there must be a simpler way to write that...

((1/(1-inflation))-1) / ROI = ((1/(1-.03))-1)/.06 = 51.6%

PS: Just keeping what left over when you subtract the inflation rate from your ROI is close and you don't actually know the inflation rate or your long term ROI most of the time.

Got it. Thanks!

I think you're missing the point of his blog. The entire premise is that by cutting your expenses, living within your means, and some clever hacking, you can be "free". I can certainly see how 4K would be FU money, say, if I moved to a low cost economy like Thailand, Costa Rica, or even middle America.

the entire blog I mean, not just this post

$48,000/yr is easily enough to count, when it comes on top of whatever income you need to live on. I've seen people end up having to get a job, or take out a loan, or acquire some other millstone round their neck, for want of much less.

It's highly dependent on local costs of living. And if it doesn't require full-time maintenance, allowing one to work (or not) on whatever one chooses while still collecting a comfortable income, that is absolutely FU money.

The point of his blog is to demonstrate how to make the realm of FU money easier to achieve. His major claim is that, since he owns his house and has chosen a relatively low-cost region to live in, his yearly expenses for his entire family are around $27,000. So agreed, for him $4k/month of free money would definitely qualify.