B1/B2 Travel qn

[Pricey]

Currently, my friend has a B1/B2 valid & active visa. He has travelled to the US on business 3-4 times in the past (almost an annual visit over the past 5 years or so). He wishes to visit this time for pleasure/ as a tourist for about two weeks to reunite with a couple old friends.
 Could he travel to the US on this active B1/B2 visa for pleasure?
 What are the odds that his entry would be restricted?
 What documents must he bring with him, in case questioned at entry (with the exception of the passport detailing the active visa)?
Thank you much!

[immihelp]

1. Yes.
2. Should be fine.
3. Return air ticket and travel medical insurance, available at https://www.insubuy.com/