Is a business centered around making sports predictions illegal?

I have a friend, who is really good at predicting the outcome of
games, who is interested in predicting sporting events for a fee
($5-$50).  Is it illegal in the United States to create a website
(hosted in the US) and sell the predictions online?

You might want to wait for a definitive answer from someone else, but
I'd definitely say no. After all, all you are doing is selling your
opinion - what people do with it is not your responsibility.

There are plenty of sports handicappers online (search: sports picks)
who charge money for their insights - although I didn't check where
they were based. Some include a little disclaimer ("for entertainment
purposes only") just to absolutely cover themselves.

But consider this: if your friend really can pick games (to some
significant degree above 50/50) why would you want to sell this
information? If it were me, I'd save up a little bankroll and just
gamble my own way to riches.

I mean, it's a little like the guy next to you at the bar leaning over
and saying "You know, I've got a system whereby you can make thousands
of dollars with virtually no effort. And I'll sell it to you for $
20".

Have a good day.