What exactly does a Series 65 allow someone to do?

Asking for a friend

My friend is seeking to trade stocks with both of their money

I’ve got a friend. He knows a guy who wants to invest in him (my friend) . He’s decided to start a company and get a Series 65 to set up a fee structure.

Is it legal for my friend to receive funds to invest for the guy he knows? (Once he has an LLC and a Series 65?)

He has read that the Series 65 holder can’t charge commission. Now he’s confused.

Also where would my friend take the test? And study?

If this belongs on a different subreddit, let me know. Thanks