Traditional IRA/401k accounts
require distributions to begin by age 70 1/2. You can start them earlier. You may begin them with no penalty at age 59 1/2. Distributions from Traditional IRAs prior to age 59½ are subject to a 10% penalty, in addition to applicable federal and state taxes. Under certain circumstances, you may be able to avoid the penalty on early withdrawals. Common exceptions include:
First-time home purchase
Qualified education expenses
Death or disability
Unreimbursed medical expenses
Health insurance, if you're unemployed
You are not using these accounts for early retirement funding, however. You should also be funding things like Roth IRAs, taxable accounts, HSAs, in addition to 401k/traditional IRAs. Roth IRA
contributions can be withdrawn penalty free any time. Taxable accounts proceeds (both the contributions and the growth/LTCG/dividends can be withdrawn any time as long as you pay the taxes (if any owed - i.e. you are above a 15% taxable bracket).
And no one says you can't touch the traditional IRA/401k - just that you have to pay 10% on whatever you withdraw if you take it out before you're 59. But the common thought is to use traditional IRA/401k accounts as your "old person" money; these accounts are the ones you just leave alone in early retirement and let grow. You use Roth/taxable/HSA in early retirement for expenses.
http://forum.mrmoneymustache.com/investor-alley/investment-order-65299/http://www.mrmoneymustache.com/2011/11/11/how-much-is-too-much-in-your-401k/http://www.madfientist.com/how-to-access-retirement-funds-early/