The bolded issue does not matter, and is no concern of the US. The only concern of the US is whether he paid taxes. Getting paid for services not rendered would be a matter for Burisma stakeholders.
Silverado Savings & Loan hired Neil Bush because of who is father was. This happens all the time. It is not against the law. Silverado, like most S&L's at the time, crashed and burned. Neil Bush ended up doing little but embarrassing his father, which is pretty much all that Hunter Biden at Burisma has done.
Financial Scams and the Bush Family: The Savings & Loan Scandal, the BCCI, the Mexican Drug Cartel, NAFTA - Global ResearchGlobal Research - Centre for Research on Globalization
What would be against the law is actions of the father in using the power of his position to provide favors for the son contrary to US policy. There is no evidence of that. Let us start with the fact that a Vice President of the United States doesn't really have all that much power, which makes this whole thing silly..... other than, its yet another brilliant example of Trump deflecting from his own corruption by shinning the light in another direction.
Any thoughts on how much Eric, Don Jr, Ivanka and Jared have made because of the Trump presidency?