There's somewhere between a "lifestyle business" and a unicorn though. You can be a contractor with a focus on re-doing roofs and pull in $1m/year without too much work once you have things running. You will be wealthy, but you won't ever pull in $20m/year. I think it's fair to call that a "lifestyle business".

I know of a company near me that has $300M/year revenue (gross, not net) that sells cables and other equipment to ISPs in the region. It's owned by one person. I don't know their margins, but that person might be making $20M/year. They might be able to grow that business and sell it for $500M dollars if they play their cards right. I wouldn't call that a "lifestyle" or "small" business. It's somewhere in the middle.

I think it's the latter type that the article is referring to.