I have a foreign client who resides in his native country who comes to the US a number of times a year for about a week each time. He wants to start a magazine in the US. I can set up an LLC for him and get the LLC an EIN. The magazine will be produced in his country, delivered to the US for sale in various locations.

My question: since the client will get a K1 from the LLC I suppose I need to help him get an ITIN, correct?

His native country has a tax treaty with the US. So do I have him check "a" as the reason for the ITIN?

This may not apply to this matter, but I was looking at the exceptions for when one does not have to file a tax return with the ITIN application, but since LLC's can elect to be treated as pass through entities for tax purposes, can exception 1a apply to individuals who are members of an LLC which invests in the US?

Correct; an ITIN will be needed.

As for the reason, "b" would be more appropriate, because, eventually, your client will need to file a non-resident (Form 1040NR or 1040NR-EZ) tax return.

As for the final issue, I do not believe that exception applies. The LLC is a pass-through entity, so the profits WILL pass through to your client, who, again, will need to file a non-resident (Form 1040NR or 1040NR-EZ) tax return.