The safe withdrawal rate -- that is, the rate at which you can withdraw from retirement accounts without too much risk of running out of money eventually -- is generally considered to be around 4%. With $900,000 saved up, that means the OP can spend about $36,000 / year from his nest egg without too much risk. The article states that they live as if they made $35,000 - $40,000 / year. So the income from their retirement combined with their side business should be enough to at least sustain their current lifestyle. I have no idea if their $35,000 - $40,000 estimate covers health insurance, so it's hard to say whether they are at risk of being wiped out by medical expenses.