We need some more information:

- What airline is he coming in on?
- What airline is he going out on?
- Is this booked on a single ticket, or on separate tickets?
- Is he checking any luggage, or just carrying on?
- US Citizen? Global Entry? ...?

In general, he'll get off the plane, proceed through passport control and then collect his checked bags. After collecting the bags, he'll take them (along with his entry forms [distributed/filled out on plane]) through customs/USDA inspection. This process takes anywhere from a few minutes to 2 hours depending on how busy they are.

In general, a I'd say a US citizen with no red flags should expect around 60 minutes. After that, you're like anyone else coming into the airport. You walk to the terminal in question, go through TSA and go to your gate. How long this takes depends on what terminals you are going to/from. There is a bus that goes between terminals, but it may actually take longer than just walking (depending on where you board and where you need to get off).

If this is your son's first time traveling internationally, have him read through this thread to get an idea about what happens. Also map out how he has to get from point A to point B. That will give him a leg up, sometimes staff are hard to find at LAX.

As a general note -- LAX is quite possibly the worst entry point in the US. Allow for a minimum of 3 hours to connect international --> domestic. Your carrier might allow a tighter connection, but don't accept it unless you have no other options. The T6/T7 entry point (United, primarily) is definitely the worst of them all.

-- Dan