He said he paid no income tax.
If he's in the UK, he probably has a small limited company and he'll pay himself his personal tax-free allowance as income and the remainder as a dividend. He's still paying 20% corporation tax on the profits, plus 22.5% on dividends that take him over 35k. Not as much as he would have paid in income tax, but he's hardly a non-taxpayer - it's just good planning if you can do it.
... or he could be using a tax avoidance scheme where he "invests" all his salary in an overseas scheme who then "loan" the money back to him. In which case, yes, that's pretty dodgy.