For those who are keen to know more, perhaps they should read some books (meant for laymen) about the subject also. Some important topics include:
1) The habit of regular savings
2) Thrift and cutting back on discretionary spending
3) Invest the excess in income producing assets that generate a stream of passive income (income that will be generated without you having to actively manage the assets or business)
4) Insurance to safeguard against uncertainties
5) Calculating how much you need (monthly expenses), which varies according to WHERE you intend to live
6) From the above, ascertain when your passive income can exceed your expenses. When you passive income exceeds your expenses and you have some emergency fund (liquid cash), you are theoretically Financially Independent because you don’t have to work a day to survive.

A very simple model might be:
1) You have a job paying US$5,000 after-tax salary.
2) You pay off your debts asap. So the $5k can be used to pay for your expenses + savings
3) You reduce your expenses and set a target saving rate, say $3,000/m.
4) You invest your $36k/y in assets that generate passive income. For example, stocks, bonds or property.
5) You ascertain that you want to live in Southeast Asia most time, and that you need US$10,000/y.
6) To derive the $10k/y, you could, for example,
a) own a property costing $150k and rent it
b) keep a stock and bond mutual fund of $250K and withdraw 4% pa from it
c) purchase an annuity with a single consideration of $180K, for which the insurance company promises to pay you a guaranteed $10k/year for as long as you live, plus a variable bonus

Of course, the above 3 examples differ in their levels of effort and predictability. The first option may require some effort from you to find the tenants, collect the rental, fix the property, etc. unless you hire a friend or estate management firm to help you do these.

Option 2 requires less effort. You can park your mutual fund in an online brokerage and instructs it to remit the withdrawals of 4% electronically to your bank, and access the money with your debit/ATM card from any major town or city with an ATM machine. But the 4% is projected, not guaranteed, to be sustainable, based on historical data.

Option 3 is the most predictable because you are guaranteed the $10k every year plus some bonuses. But you may not be able to withdraw the fund for emergency use like you could if you had invested in a mutual fund instead. But it may also be its most important advantage since you do not want to play with your income source. If you could withdraw it, you may spend it away and lose the goose that lays the golden eggs.Similarly, you can instruct the insurance company to pay the annuity pay-outs to your card-linked bank account and withdraw that income wherever you are.

Having dealt with the income, you might, of course, want to save a little more which you can use for emergency. But if you want too much emergency fund, you may procrastinate the transition to nomadic lifestyle.

After reading the blogs of several nomads, it seems that it is quite manageable for them to live on US$10k/y, so the above examples may give you a clue as to how much you really need to become a nomad yourself. Perhaps $180k in an annuity plus some allowance in mutual funds and money market funds (cash-like investment) could work. Of course, knowing that the US$ is likely to depreciate due to the enormous debt the US is having, it’s more advisable to park your annuity in one or two countries whose governments are fiscally responsible and sound, and whose currencies are likely to appreciate over time. Good examples would be politically neutral & stable small states such as Switzerland & Singapore. With a Swiss or Singaporean annuity, some investments in a balanced and globally diversified mutual fund and some liquid assets like bank deposit, you could be assured of a steady stream of income for as long as your live, plus some allowance for emergencies. If you also have some insurance, you would have additional protection.

Many experts have suggested that the past decades of growth had been sustained with US debts, and that the coming years may see a depression to correct the irrational exuberance. This forecast is economically sound. So, I’d play safe by parking at least half if not all of my income producing fund into a low-risk investment like annuity in order to secure a guaranteed stream of income. If growth will be slow in the coming years, then my investment in mutual funds may not be sustainable if I withdraw 4-5% every year from it for years. It may shrink, and I may be forced out of retirement in this worst case scenario.

For those who are keen in full instead of semi-retirement, the above provides some insights into how to plan for that ultimate day when you can become theoretically Financially Independent.