Business A is being run as a "lifestyle" business and the owner/CEO is not on the payroll, but instead has been using another entity he owns (Biz B) to charge "professional services" to Biz A.

Is this common?

Given this practice, are there other things common with this type of operator I need to look out for that wouldn't be obvious in the financials?

I'm assuming that his gigantic fees ($500k on $2M Rev) have had the benefit of avoiding Biz A from paying income taxes on his "services".